1.
Atom
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An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms, Atoms are very small, typical sizes are around 100 picometers. Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more bound to the nucleus. The nucleus is made of one or more protons and typically a number of neutrons. Protons and neutrons are called nucleons, more than 99. 94% of an atoms mass is in the nucleus. The protons have an electric charge, the electrons have a negative electric charge. If the number of protons and electrons are equal, that atom is electrically neutral, if an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion. The electrons of an atom are attracted to the protons in a nucleus by this electromagnetic force. The number of protons in the nucleus defines to what chemical element the atom belongs, for example, the number of neutrons defines the isotope of the element. The number of influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the changes observed in nature. The idea that matter is made up of units is a very old idea, appearing in many ancient cultures such as Greece. The word atom was coined by ancient Greek philosophers, however, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what look like. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, in the early 1800s, John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers
2.
Gamma ray
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Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon
3.
Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
4.
Internal conversion
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Internal conversion is a radioactive decay process wherein an excited nucleus interacts electromagnetically with one of the orbital electrons of the atom. This causes the electron to be emitted from the atom, thus, in an internal conversion process, a high-energy electron is emitted from the radioactive atom, but not from the nucleus. Internal conversion is possible whenever gamma decay is possible, except in the case where the atom is fully ionised, during internal conversion, the atomic number does not change, and thus no transmutation of one element to another takes place. The atom thus emits high-energy electrons and X-ray photons, none of which originate in that nucleus, the atom supplied the energy needed to eject the electron, which in turn caused the latter events and the other emissions. Whereas the energy spectrum of beta particles plots as a broad hump, in the quantum mechanical model of the electron, there is a finite probability of finding the electron within the nucleus. During the internal process, the wavefunction of an inner shell electron is said to penetrate the volume of the atomic nucleus. When this happens, the electron may couple to an energy state of the nucleus and take the energy of the nuclear transition directly. The kinetic energy of the electron is equal to the transition energy in the nucleus, minus the binding energy of the electron to the atom. Most internal conversion electrons come from the K shell, as two electrons have the highest probability of being within the nucleus. However, the s states in the L, M, and N shells are also able to couple to the nuclear fields, ratios of K-shell to other L, M, or N shell internal conversion probabilities for various nuclides have been prepared. After the IC electron has been emitted, the atom is left with a vacancy in one of its electron shells, usually an inner one. This hole will be filled with an electron from one of the higher shells, consequently, one or more characteristic X-rays or Auger electrons will be emitted as the remaining electrons in the atom cascade down to fill the vacancies. The decay scheme on the shows that 203Hg produces a continuous beta spectrum with maximum energy 214 keV. This state decays very fast to the state of 203Tl. The figure on the shows the electron spectrum of 203Hg. You can see the continuous spectrum and also the K-, L-. Since the binding energy of the K electrons in 203Tl amounts to 85 keV, because of lesser binding energies, the L- and M-lines have higher energies. Because of the energy resolution of the spectrometer, the lines have a Gaussian shape of finite width
5.
Particle
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A particle is a minute fragment or quantity of matter. In the physical sciences, a particle is a small localized object to which can be ascribed several physical or chemical properties such as volume or mass. Particles can also be used to create models of even larger objects depending on their density. The term particle is rather general in meaning, and is refined as needed by various scientific fields, something that is composed of particles may be referred to as being particulate. However, the particulate is most frequently used to refer to pollutants in the Earths atmosphere. The concept of particles is particularly useful when modelling nature, as the treatment of many phenomena can be complex. It can be used to make simplifying assumptions concerning the processes involved, francis Sears and Mark Zemansky, in University Physics, give the example of calculating the landing location and speed of a baseball thrown in the air. The treatment of large numbers of particles is the realm of statistical physics, the term particle is usually applied differently to three classes of sizes. The term macroscopic particle, usually refers to particles much larger than atoms and these are usually abstracted as point-like particles, or even invisible. This is even though they have volumes, shapes, structures, examples of macroscopic particles would include powder, dust, sand, pieces of debris during a car accident, or even objects as big as the stars of a galaxy. Another type, microscopic particles usually refers to particles of sizes ranging from atoms to molecules, such as carbon dioxide, nanoparticles and these particles are studied in chemistry, as well as atomic and molecular physics. The smallest of particles are the particles, which refer to particles smaller than atoms. These particles are studied in particle physics, because of their extremely small size, the study of microscopic and subatomic particles fall in the realm of quantum mechanics. Particles can also be classified according to composition, composite particles refer to particles that have composition – that is particles which are made of other particles. For example, an atom is made of six protons, eight neutrons. By contrast, elementary particles refer to particles that are not made of other particles, according to our current understanding of the world, only a very small number of these exist, such as the leptons, quarks or gluons. However it is possible some of these might turn up to be composite particles after all. While composite particles can very often be considered point-like, elementary particles are truly punctual, both elementary and composite particles, are known to undergo particle decay
6.
Alpha particle
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Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They are generally produced in the process of decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a helium ion with a +2 charge. If the ion gains electrons from its environment, the particle can be written as a normal helium atom 4 2He. Some science authors may use doubly ionized helium nuclei and alpha particles as interchangeable terms, the nomenclature is not well defined, and thus not all high-velocity helium nuclei are considered by all authors to be alpha particles. As with beta and gamma rays/particles, the used for the particle carries some mild connotations about its production process and energy. Thus, alpha particles may be used as a term when referring to stellar helium nuclei reactions. A higher energy version of alphas than produced in alpha decay is a product of an uncommon nuclear fission result called ternary fission. However, helium nuclei produced by particle accelerators are less likely to be referred to as alpha particles, alpha particles, like helium nuclei, have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have an energy of about 5 MeV. They are a highly ionizing form of radiation, and have low penetration depth. They are able to be stopped by a few centimeters of air, however, so-called long range alpha particles from ternary fission are three times as energetic, and penetrate three times as far. To a lesser extent, this is true of very high-energy helium nuclei produced by particle accelerators. The best-known source of particles is alpha decay of heavier atoms. When an atom emits an alpha particle in alpha decay, the mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by two, as a result of the loss of two protons – the atom becomes a new element. Examples of this sort of nuclear transmutation are when uranium becomes thorium, or radium becomes radon gas, alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements
7.
Beta particle
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Two forms of beta decay, β− and β+, respectively produce electrons and positrons. Beta particles are a type of ionizing radiation, the neutron turns into a proton through the emission of a virtual W− boson. At the quark level, W− emission turns a down quark into an up quark, the virtual W− boson then decays into an electron and an antineutrino. Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors, free neutrons also decay via this process. Both of these contribute to the copious numbers of beta rays. The daughter nucleus is a lower-energy state, of the three common types of radiation given off by radioactive materials, alpha, beta and gamma, beta has the medium penetrating power and the medium ionising power. Although the beta particles given off by different radioactive materials vary in energy, shielding composed of materials with lower atomic weight generates gammas with lower energy, making such shields somewhat more effective per unit mass than ones made of high-Z materials such as lead. Being composed of charged particles, beta radiation is more strongly ionizing than gamma radiation, when passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off bremsstrahlung x-rays. In water, beta radiation from nuclear fission products typically exceeds the speed of light in that material. The intense beta radiation from the rods of pool-type reactors can thus be visualized through the transparent water that covers. The ionizing or excitation effects of particles on matter are the fundamental processes by which radiometric detection instruments detect. The ionization of gas is used in ion chambers and Geiger-Muller counters, beta particles can be used to treat health conditions such as eye and bone cancer and are also used as tracers. Strontium-90 is the material most commonly used to produce beta particles, beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the radiation is absorbed while passing through the product. If the product is too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the paper will then move the rollers to change the thickness of the final product. An illumination device called a betalight contains tritium and a phosphor, as tritium decays, it emits beta particles, these strike the phosphor, causing the phosphor to give off photons, much like the cathode ray tube in a television. Beta-plus decay of a radioactive isotope is the source of the positrons used in positron emission tomography
8.
Radioactive decay
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A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating, the half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe. A radioactive nucleus with spin can have no defined orientation. If there are multiple particles produced during a single decay, as in decay, their relative angular distribution. Such a parent process could be a previous decay, or a nuclear reaction, the decaying nucleus is called the parent radionuclide, and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from an excited state. When the number of changes, an atom of a different chemical element is created. The first decay processes to be discovered were alpha decay, beta decay, alpha decay occurs when the nucleus ejects an alpha particle. This is the most common process of emitting nucleons, but highly excited nuclei can eject single nucleons, or in the case of cluster decay, specific light nuclei of other elements. Beta decay occurs when the nucleus emits an electron or positron, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these result in a well-defined nuclear transmutation. By contrast, there are radioactive decay processes that do not result in a nuclear transmutation, another type of radioactive decay results in products that vary, appearing as two or more fragments of the original nucleus with a range of possible masses. For a summary table showing the number of stable and radioactive nuclides in each category, there are 29 naturally occurring chemical elements on Earth that are radioactive. They are those that contain 34 radionuclides that date before the time of formation of the solar system, well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel and these materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it, all results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper and these radiations were given the name Becquerel Rays
9.
Ionizing radiation
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Ionizing radiation is radiation that carries enough energy to free electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic particles, ions or atoms moving at high speeds. The boundary between ionizing and non-ionizing electromagnetic radiation that occurs in the ultraviolet is not sharply defined, since different molecules, conventional definition places the boundary at a photon energy between 10 eV and 33 eV in the ultraviolet. Typical ionizing subatomic particles from radioactivity include alpha particles, beta particles, almost all products of radioactive decay are ionizing because the energy of radioactive decay is typically far higher than that required to ionize. Cosmic rays are generated by stars and certain events such as supernova explosions. Cosmic rays may also produce radioisotopes on Earth, which in turn decay, cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth referred to as background radiation. Ionizing radiation can also be generated artificially using X-ray tubes, particle accelerators, ionizing radiation is invisible and not directly detectable by human senses, so radiation detection instruments such as Geiger counters are required to detect it. However, it can cause emission of light upon interaction with matter, such as in Cherenkov radiation. Exposure to ionizing radiation damage to living tissue, and can result in mutation, radiation sickness, cancer. Ionizing radiation is categorized by the nature of the particles or electromagnetic waves that create the ionizing effect and these have different ionization mechanisms, and may be grouped as directly or indirectly ionizing. Any charged massive particle can ionize atoms directly by fundamental interaction through the Coulomb force if it carries sufficient kinetic energy and this includes atomic nuclei, electrons, muons, charged pions, protons, and energetic charged nuclei stripped of their electrons. When moving at relativistic speeds these particles have enough energy to be ionizing. For example, an alpha particle is ionizing, but moves at about 5% c. Natural cosmic rays are made up primarily of protons but also include heavier atomic nuclei like helium ions. Pions can also be produced in large amounts in particle accelerators, alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particle emissions are produced in the process of alpha decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a Helium ion with a +2 charge
10.
Half-life
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Half-life is the time required for a quantity to reduce to half its initial value. The term is used in nuclear physics to describe how quickly unstable atoms undergo. The term is used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs, the converse of half-life is doubling time. The original term, half-life period, dating to Ernest Rutherfords discovery of the principle in 1907, was shortened to half-life in the early 1950s. Rutherford applied the principle of a radioactive elements half-life to studies of age determination of rocks by measuring the period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed. A half-life usually describes the decay of discrete entities, such as radioactive atoms, in that case, it does not work to use the definition that states half-life is the time required for exactly half of the entities to decay. For example, if there are 3 radioactive atoms with a half-life of one second, instead, the half-life is defined in terms of probability, Half-life is the time required for exactly half of the entities to decay on average. In other words, the probability of a radioactive atom decaying within its half-life is 50%, for example, the image on the right is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the remaining, only approximately. Nevertheless, when there are many identical atoms decaying, the law of large numbers suggests that it is a good approximation to say that half of the atoms remain after one half-life. There are various simple exercises that demonstrate probabilistic decay, for example involving flipping coins or running a computer program. The three parameters t1⁄2, τ, and λ are all related in the following way. Amount approaches zero as t approaches infinity as expected, some quantities decay by two exponential-decay processes simultaneously. There is a half-life describing any exponential-decay process, for example, The current flowing through an RC circuit or RL circuit decays with a half-life of RCln or lnL/R, respectively. For this example, the half time might be used instead of half life. In a first-order chemical reaction, the half-life of the reactant is ln/λ, in radioactive decay, the half-life is the length of time after which there is a 50% chance that an atom will have undergone nuclear decay
11.
Exponential decay
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A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the differential equation. The solution to this equation is, N = N0 e − λ t, where N is the quantity at time t, and N0 = N is the initial quantity, i. e. the quantity at time t =0. If the decaying quantity, N, is the number of elements in a certain set. This is called the lifetime, τ, and it can be shown that it relates to the decay rate, λ, in the following way. For example, if the population of the assembly, N, is 1000. A very similar equation will be seen below, which arises when the base of the exponential is chosen to be 2, in that case the scaling time is the half-life. A more intuitive characteristic of exponential decay for many people is the time required for the quantity to fall to one half of its initial value. This time is called the half-life, and often denoted by the symbol t1/2, the half-life can be written in terms of the decay constant, or the mean lifetime, as, t 1 /2 = ln λ = τ ln . When this expression is inserted for τ in the equation above, and ln 2 is absorbed into the base. Thus, the amount of left is 2−1 = 1/2 raised to the number of half-lives that have passed. Thus, after 3 half-lives there will be 1/23 = 1/8 of the material left. Therefore, the mean lifetime τ is equal to the half-life divided by the log of 2, or. E. g. polonium-210 has a half-life of 138 days, the equation that describes exponential decay is d N d t = − λ N or, by rearranging, d N N = − λ d t. This is the form of the equation that is most commonly used to describe exponential decay, any one of decay constant, mean lifetime, or half-life is sufficient to characterise the decay. The notation λ for the constant is a remnant of the usual notation for an eigenvalue. In this case, λ is the eigenvalue of the negative of the operator with N as the corresponding eigenfunction. The units of the constant are s−1
12.
Nuclear reactor
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This article is a subarticle of Nuclear power. A nuclear reactor, formerly known as a pile, is a device used to initiate. Nuclear reactors are used at power plants for electricity generation. Heat from nuclear fission is passed to a fluid, which runs through steam turbines. These either drive a ships propellers or turn electrical generators, Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, some are run only for research. As of April 2014, the IAEA reports there are 435 nuclear power reactors in operation, when a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more nuclei, releasing kinetic energy, gamma radiation, and free neutrons. A portion of neutrons may later be absorbed by other fissile atoms and trigger further fission events, which release more neutrons. This is known as a chain reaction. To control such a chain reaction, neutron poisons and neutron moderators can change the portion of neutrons that will go on to cause more fission. Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if monitoring detects unsafe conditions, commonly-used moderators include regular water, solid graphite and heavy water. Some experimental types of reactor have used beryllium, and hydrocarbons have been suggested as another possibility, the reactor core generates heat in a number of ways, The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms. The reactor absorbs some of the rays produced during fission. Heat is produced by the decay of fission products and materials that have been activated by neutron absorption. This decay heat-source will remain for some even after the reactor is shut down. A kilogram of uranium-235 converted via nuclear processes releases approximately three times more energy than a kilogram of coal burned conventionally. A nuclear reactor coolant — usually water but sometimes a gas or a metal or molten salt — is circulated past the reactor core to absorb the heat that it generates
13.
Cyclotron
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A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1934 in which charged particles accelerate outwards from the centre along a spiral path. The particles are held to a spiral trajectory by a magnetic field. Lawrence was awarded the 1939 Nobel prize in physics for this invention, the largest single-magnet cyclotron was the 4.67 m synchrocyclotron built between 1940 and 1946 by Lawrence at the University of California at Berkeley, which could accelerate protons to 730 MeV. The largest cyclotron is the 17.1 m multimagnet TRIUMF accelerator at the University of British Columbia in Vancouver, there are over 1200 cyclotrons used in nuclear medicine worldwide for the production of radionuclides. The cyclotron was conceived in Germany in the 1920s, at Aachen University in 1926, the cyclotron was proposed by a co-student of Rolf Widerøe, who rejected the idea as too complicated to construct. In 1927, Max Steenbeck developed the concept of the cyclotron at Siemens, the first cyclotron patent was filed by Hungarian physicist Leo Szilard in 1929, while working at Humboldt University of Berlin. The cyclotron was developed and patented by Ernest Lawrence of the University of California, Berkeley. Lawrence went on to make a working cyclotron using large electromagnets from Poulsen arc radio transmitters provided by the Federal Telegraph Company. A graduate student, M. Stanley Livingston, did much of the work of translating the idea into working hardware, Lawrence read an article about the concept of a drift tube linac by Rolf Widerøe, who had also been working along similar lines with the betatron concept. He also developed a 467 cm synchrocyclotron, the first European cyclotron was constructed in Leningrad in the physics department of the Radium Institute, headed by Vitaly Khlopin. This Leningrad instrument was first proposed in 1932 by George Gamow and Lev Mysovskii and was installed, in Nazi Germany a cyclotron was built in Heidelberg under supervision of Walther Bothe and Wolfgang Gentner, with support from the Heereswaffenamt, and became operative in 1943. A cyclotron accelerates a charged particle beam using a high alternating voltage which is applied between two hollow D-shaped sheet metal electrodes called dees inside a vacuum chamber. The dees are placed face to face with a gap between them, creating a cylindrical space within them for the particles to move. The particles are injected into the center of this space, the dees are located between the poles of a large electromagnet which applies a static magnetic field B perpendicular to the electrode plane. The magnetic field causes the path to bend in a circle due to the Lorentz force perpendicular to their direction of motion. If the particles speed were constant, they would travel in a path within the dees under the influence of the magnetic field. However a radio frequency alternating voltage of several thousand volts is applied between the dees, the frequency is set so that the particles make one circuit during a single cycle of the voltage. Each time after the pass to the other dee electrode the polarity of the RF voltage reverses
14.
Particle accelerator
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A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to nearly light speed and to contain them in well-defined beams. Large accelerators are used in physics as colliders, or as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world, there are two basic classes of accelerators, electrostatic and electrodynamic accelerators. Electrostatic accelerators use electric fields to accelerate particles. The most common types are the Cockcroft–Walton generator and the Van de Graaff generator, a small-scale example of this class is the cathode ray tube in an ordinary old television set. The achievable kinetic energy for particles in these devices is determined by the accelerating voltage, electrodynamic or electromagnetic accelerators, on the other hand, use changing electromagnetic fields to accelerate particles. Since in these types the particles can pass through the accelerating field multiple times. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators, because colliders can give evidence of the structure of the subatomic world, accelerators were commonly referred to as atom smashers in the 20th century. Despite the fact that most accelerators actually propel subatomic particles, the term persists in popular usage when referring to particle accelerators in general. Beams of high-energy particles are useful for both fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research and it has been estimated that there are approximately 30,000 accelerators worldwide. The bar graph shows the breakdown of the number of industrial accelerators according to their applications, for the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV, and the interactions of the simplest kinds of particles, leptons and quarks for the matter, the largest and highest energy particle accelerator used for elementary particle physics is the Large Hadron Collider at CERN, operating since 2009. These investigations often involve collisions of heavy nuclei – of atoms like iron or gold – at energies of several GeV per nucleon, the largest such particle accelerator is the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. An example of type of machine is LANSCE at Los Alamos. A large number of light sources exist worldwide. The ESRF in Grenoble, France has been used to extract detailed 3-dimensional images of trapped in amber. Thus there is a demand for electron accelerators of moderate energy. Everyday examples of particle accelerators are cathode ray tubes found in television sets and these low-energy accelerators use a single pair of electrodes with a DC voltage of a few thousand volts between them
15.
Primordial nuclide
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In geochemistry and geonuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. They are the stable nuclides plus the long-lived fraction of radionuclides surviving in the solar nebula through planet accretion until the present. Only 286 such nuclides are known, all of the known 254 stable nuclides occur as primordial nuclides, plus another 32 nuclides that have half-lives long enough to have survived from the formation of the Earth. These 32 primordial radionuclides represent isotopes of 27 separate elements, cadmium, tellurium, neodymium, samarium and uranium each have two primordial radioisotopes. Because the age of the Earth is 4. 58×109 years and these are the 4 nuclides with half-lives comparable to, or less than, the estimated age of the universe. For a complete list of the 32 known primordial radionuclides, including the next 28 with half-lives much longer than the age of the universe, the next longest-living nuclide after the end of the list given in the table is 244Pu, with a half-life of 8. 08×107 years. It has been reported to exist in nature as a primordial nuclide, likewise, the second-longest-lived non-primordial 146Sm, was once reported as primordial, but this could not be replicated. Taking into account that all these nuclides must exist since at least 4. 6×109 years, meaning survive 57 half-lives, there exist many extremely long-lived nuclides whose half-lives are still unknown. Nevertheless, the number of nuclides with half-lives so long that they cannot be measured with present instruments—and are considered from this viewpoint to be stable nuclides—is limited, because primordial chemical elements often consist of more than one primordial isotope, there are only 84 distinct primordial chemical elements. Of these,80 have at least one stable isotope. Some unstable isotopes which occur naturally are not primordial, as they must be constantly regenerated and this occurs by cosmic radiation, or by such processes as geonuclear transmutation. Other examples of naturally occurring but non-primordial nuclides are radon, polonium, and radium. A similar radiogenic series is derived from the radioactive primordial nuclide thorium-232. All of such nuclides have shorter half-lives than their parent radioactive primordial nuclides, there are about 51 nuclides which are radioactive and exist naturally on Earth but are not primordial. There are 254 stable primordial nuclides and 32 radioactive primordial nuclides, bismuths half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The numbers of elements are smaller, because many primordial elements are represented by more than one primordial nuclide, see chemical element for more information. As noted, these number about 254, for a list, see the article list of stable isotopes. For a complete list noting which of the stable 254 nuclides may be in some respect unstable, see list of nuclides and stable isotope
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Stable nuclide
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Stable nuclides are nuclides that are not radioactive and so do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, the 80 elements with one or more stable isotopes comprise a total of 254 nuclides that have not been known to decay using current equipment. Of these elements,26 have only one isotope, they are thus termed monoisotopic. The rest have more than one stable isotope, tin has ten stable isotopes, the largest number known for an element. Most naturally occurring nuclides are stable, and about 32 more are known radioactives with sufficiently long half-lives to occur primordially. If the half-life of a nuclide is comparable to, or greater than, the Earths age, a significant amount will have survived since the formation of the Solar System and it will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years and this is the present limit of detection, as shorter-lived nuclides have not yet been detected undisputedly in nature. Some isotopes that are classed as stable are predicted to have extremely long half-lives, 209Bi and 180W were formerly classed as stable, but have been recently found to be alpha-active. However, such nuclides do not change their status as primordial when they are found to be radioactive. Most stable isotopes in the earth are believed to have formed in processes of nucleosynthesis, either in the Big Bang. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides and these decay-products are termed radiogenic isotopes, in order to distinguish them from the much larger group of non-radiogenic isotopes. The so-called island of stability may reveal a number of long-lived or even stable atoms that are heavier than lead, of the known chemical elements,80 elements have at least one stable nuclide. These comprise the first 82 elements from hydrogen to lead, with the two exceptions, technetium and promethium, that do not have any stable nuclides, as of December 2011, there were a total of 254 known stable nuclides. In this definition, stable means a nuclide that has never observed to decay against the natural background. Thus, these elements have half lives too long to be measured by any means and these last 26 are thus called monoisotopic elements. The mean number of isotopes for elements which have at least one stable isotope is 254/80 =3.2. Stability of isotopes is affected by the ratio of protons to neutrons, as in the case of tin, a magic number for Z, the atomic number, tends to increase the number of stable isotopes for the element. Just as in the case of electrons, which have the lowest energy state when they occur in pairs in an orbital, nucleons exhibit a lower energy state when their number is even
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Chemical element
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A chemical element or element is a species of atoms having the same number of protons in their atomic nuclei. There are 118 elements that have identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes, iron is the most abundant element making up Earth, while oxygen is the most common element in the Earths crust. Chemical elements constitute all of the matter of the universe. The two lightest elements, hydrogen and helium, were formed in the Big Bang and are the most common elements in the universe. The next three elements were formed mostly by cosmic ray spallation, and are rarer than those that follow. Formation of elements with from 6 to 26 protons occurred and continues to occur in main sequence stars via stellar nucleosynthesis, the high abundance of oxygen, silicon, and iron on Earth reflects their common production in such stars. The term element is used for atoms with a number of protons as well as for a pure chemical substance consisting of a single element. A single element can form multiple substances differing in their structure, when different elements are chemically combined, with the atoms held together by chemical bonds, they form chemical compounds. Only a minority of elements are found uncombined as relatively pure minerals, among the more common of such native elements are copper, silver, gold, carbon, and sulfur. All but a few of the most inert elements, such as gases and noble metals, are usually found on Earth in chemically combined form. While about 32 of the elements occur on Earth in native uncombined forms. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, the history of the discovery and use of the elements began with primitive human societies that found native elements like carbon, sulfur, copper and gold. Later civilizations extracted elemental copper, tin, lead and iron from their ores by smelting, using charcoal, alchemists and chemists subsequently identified many more, almost all of the naturally occurring elements were known by 1900. Save for unstable radioactive elements with short half-lives, all of the elements are available industrially, almost all other elements found in nature were made by various natural methods of nucleosynthesis. On Earth, small amounts of new atoms are produced in nucleogenic reactions, or in cosmogenic processes. Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope, Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected, the very heaviest elements undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized
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Hydrogen
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Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity
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Tritium
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Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons, naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. It can be produced by irradiating lithium metal or lithium bearing ceramic pebbles in a nuclear reactor, the name of this isotope is derived from the Greek word τρίτος meaning third. While tritium has several different experimentally determined values of its half-life and it decays into helium-3 by beta decay as in this nuclear equation, and it releases 18.6 keV of energy in the process. The electrons kinetic energy varies, with an average of 5.7 keV, beta particles from tritium can penetrate only about 6.0 mm of air, and they are incapable of passing through the dead outermost layer of human skin. The unusually low energy released in the beta decay makes the decay appropriate for absolute neutrino mass measurements in the laboratory. The low energy of tritiums radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting, Tritium is produced in nuclear reactors by neutron activation of lithium-6. This is possible with neutrons of any energy, and is an exothermic reaction yielding 4.8 MeV, in comparison, the fusion of deuterium with tritium releases about 17.6 MeV of energy. High-energy neutrons can produce tritium from lithium-7 in an endothermic reaction. This was discovered when the 1954 Castle Bravo nuclear test produced a high yield. High-energy neutrons irradiating boron-10 will also produce tritium, A more common result of boron-10 neutron capture is 7Li. The reactions requiring high neutron energies are not attractive production methods for peaceful applications, Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making water a good neutron moderator. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. Ontario Power Generations Tritium Removal Facility processes up to 2,500 tonnes of water a year. Deuteriums absorption cross section for thermal neutrons is about 0.52 millibarns, whereas that of oxygen-16 is about 0.19 millibarns and that of oxygen-17 is about 240 millibarns. Tritium is a product of the nuclear fission of uranium-235, plutonium-239. The release or recovery of tritium needs to be considered in the operation of reactors, especially in the reprocessing of nuclear fuels
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Lead
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Lead is a chemical element with atomic number 82 and symbol Pb. When freshly cut, it is bluish-white, it tarnishes to a dull gray upon exposure to air and it is a soft, malleable, and heavy metal with a density exceeding that of most common materials. Lead has the second-highest atomic number of the stable elements. Lead is a relatively unreactive post-transition metal and its weak metallic character is illustrated by its amphoteric nature and tendency to form covalent bonds. Compounds of lead are found in the +2 oxidation state. Exceptions are mostly limited to organolead compounds, like the lighter members of the group, lead exhibits a tendency to bond to itself, it can form chains, rings, and polyhedral structures. Lead is easily extracted from its ores and was known to people in Western Asia. A principal ore of lead, galena, often bears silver, Lead production declined after the fall of Rome and did not reach comparable levels again until the Industrial Revolution. Nowadays, global production of lead is about ten million tonnes annually, Lead has several properties that make it useful, high density, low melting point, ductility, and relative inertness to oxidation. In the late 19th century, lead was recognized as poisonous, Lead is a neurotoxin that accumulates in soft tissues and bones, damaging the nervous system and causing brain disorders and, in mammals, blood disorders. A lead atom has 82 electrons, arranged in a configuration of 4f145d106s26p2. The combined first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, leads upper neighbor in group 14. This is unusual since ionization energies generally fall going down a group as an elements outer electrons become more distant from the nucleus, the similarity is caused by the lanthanide contraction—the decrease in element radii from lanthanum to lutetium, and the relatively small radii of the elements after hafnium. The contraction is due to shielding of the nucleus by the lanthanide 4f electrons. The combined first four ionization energies of lead exceed those of tin, for this reason lead, unlike tin, mostly forms compounds in which it has an oxidation state of +2, rather than +4. Relativistic effects, which become particularly prominent at the bottom of the periodic table, as a result, the 6s electrons of lead become reluctant to participate in bonding, a phenomenon called the inert pair effect. A related outcome is that the distance between nearest atoms in crystalline lead is unusually long, the lighter group 14 elements form stable or metastable allotropes having the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals
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Technetium
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Technetium is a chemical element with symbol Tc and atomic number 43. It is the lightest element of all isotopes are radioactive. Nearly all technetium is produced synthetically, and only minute amounts are found in the Earths crust, naturally occurring technetium is a spontaneous fission product in uranium ore or the product of neutron capture in molybdenum ores. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese, many of technetiums properties were predicted by Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his table and gave the undiscovered element the provisional name ekamanganese. In 1937, technetium became the first predominantly artificial element to be produced and its short-lived gamma ray-emitting nuclear isomer—technetium-99m—is used in nuclear medicine for a wide variety of diagnostic tests. Technetium-99 is used as a source of beta particles. Long-lived technetium isotopes produced commercially are by-products of fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods, from the 1860s through 1871, early forms of the periodic table proposed by Dmitri Mendeleev contained a gap between molybdenum and ruthenium. In 1871, Mendeleev predicted this missing element would occupy the empty place below manganese and have similar chemical properties, Mendeleev gave it the provisional name ekamanganese because the predicted element was one place down from the known element manganese. Many early researchers, both before and after the table was published, were eager to be the first to discover. Its location in the table suggested that it should be easier to find than other undiscovered elements, german chemists Walter Noddack, Otto Berg, and Ida Tacke reported the discovery of element 75 and element 43 in 1925, and named element 43 masurium. The group bombarded columbite with a beam of electrons and deduced element 43 was present by examining X-ray diffraction spectrograms, the wavelength of the X-rays produced is related to the atomic number by a formula derived by Henry Moseley in 1913. The team claimed to detect a faint X-ray signal at a wavelength produced by element 43, later experimenters could not replicate the discovery, and it was dismissed as an error for many years. Still, in 1933, a series of articles on the discovery of elements quoted the name masurium for element 43, whether the 1925 team actually did discover element 43 is still debated. The discovery of element 43 was finally confirmed in a December 1936 experiment at the University of Palermo in Sicily by Carlo Perrier, in mid-1936, Segrè visited the United States, first Columbia University in New York and then the Lawrence Berkeley National Laboratory in California. He persuaded cyclotron inventor Ernest Lawrence to let him back some discarded cyclotron parts that had become radioactive. Lawrence mailed him a molybdenum foil that had part of the deflector in the cyclotron. Segrè enlisted his colleague Perrier to attempt to prove, through comparative chemistry, in 1937 they succeeded in isolating the isotopes technetium-95m and technetium-97
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Promethium
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Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive, it is one of two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements, promethium shows only one stable oxidation state of +3, however, a few +2 compounds may exist. In 1926, an Italian and an American group claimed to have isolated a sample of element 61, promethium was first produced and characterized at Oak Ridge National Laboratory in 1945 by the separation and analysis of the fission products of uranium fuel irradiated in a graphite reactor. However, a sample of the metal was only in 1963. There are two sources for natural promethium, rare decays of natural europium-151, and uranium. Because natural promethium is exceedingly scarce, it is synthesized by bombarding uranium-235 with thermal neutrons to produce promethium-147. A promethium atom has 61 electrons, arranged in the configuration 4f56s2, in forming compounds, the atom loses its two outermost electrons and one of the 4f-electrons, which belongs to an open subshell. The elements atomic radius is the third largest among all the lanthanides but is slightly greater than those of the neighboring elements. It is the exception to the general trend of the contraction of the atoms with increase of atomic radius that is not caused by the filled 4f-subshell. Many properties of promethium rely on its position among lanthanides and are intermediate between those of neodymium and samarium, promethium has a double hexagonal close packed structure and a hardness of 63 kg/mm2. This low-temperature alpha form converts into a beta, body-centered cubic phase upon heating to 890 °C, promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements. Because of its instability, chemical studies of promethium are incomplete, even though a few compounds have been synthesized, they are not fully studied, in general, they tend to be pink or red in color. Treatment of acidic solutions containing Pm3+ ions with ammonia results in a gelatinous light-brown sediment of hydroxide, Pm3, when dissolved in hydrochloric acid, a water-soluble yellow salt, PmCl3, is produced, similarly, when dissolved in nitric acid, a nitrate results, Pm3. The latter is also well-soluble, when dried, it forms pink crystals, the electron configuration for Pm3+ is 4f4, and the color of the ion is pink. The ground state term symbol is 5I4, the sulfate is slightly soluble, like the other cerium group sulfates. Cell parameters have been calculated for its octahydrate, they lead to conclusion that the density of Pm23·8 H2O is 2.86 g/cm3, the oxalate, Pm23·10 H2O, has the lowest solubility of all lanthanide oxalates. Unlike the nitrate, the oxide is similar to the corresponding samarium salt, as-synthesized, e. g. by heating the oxalate, it is a white or lavender-colored powder with disordered structure
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Pharmaceutical drug
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A pharmaceutical drug is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy is an important part of the field and relies on the science of pharmacology for continual advancement. Drugs are classified in various ways, one of the key divisions is by level of control, which distinguishes prescription drugs from over-the-counter drugs. Other ways to classify medicines are by mode of action, route of administration, biological system affected, an elaborate and widely used classification system is the Anatomical Therapeutic Chemical Classification System. The World Health Organization keeps a list of essential medicines, Drug discovery and drug development are complex and expensive endeavors undertaken by pharmaceutical companies, academic scientists, and governments. Governments generally regulate what drugs can be marketed, how drugs are marketed, controversies have arisen over drug pricing and disposal of used drugs. In the US, a drug is, A substance recognized by an official pharmacopoeia or formulary, a substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease. A substance intended to affect the structure or any function of the body, a substance intended for use as a component of a medicine but not a device or a component, part or accessory of a device. Pharmaceutical or a drug is classified on the basis of their origin, Drug from natural origin, Herbal or plant or mineral origin, some drug substances are of marine origin. Drug from chemical as well as origin, Derived from partial herbal and partial chemical synthesis Chemical. Drug derived from animal origin, For example, hormones, Drug derived from microbial origin, Antibiotics Drug derived by biotechnology genetic-engineering, hybridoma technique for example Drug derived from radioactive substances. An elaborate and widely used system is the Anatomical Therapeutic Chemical Classification System. The World Health Organization keeps a list of essential medicines, the main classes of painkillers are NSAIDs, opioids and Local anesthetics. For consciousness Some anesthetics include Benzodiazepines and Barbiturates, the main categories of drugs for musculoskeletal disorders are, NSAIDs, muscle relaxants, neuromuscular drugs, and anticholinesterases. Euthanasia is not permitted by law in countries, and consequently medicines will not be licensed for this use in those countries. Administration is the process by which a patient takes a medicine, there are three major categories of drug administration, enteral, parenteral, and other. It can be performed in various forms such as pills, tablets. There are many variations in the routes of administration, including intravenous and they can be administered all at once as a bolus, at frequent intervals or continuously
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Radiopharmaceutical
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Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs which have radioactivity. Radiopharmaceuticals can be used as diagnostic and therapeutic agents, Radiopharmacology is the branch of pharmacology that specializes in these agents. The main group of compounds are the radiotracers used to diagnose dysfunction in body tissues. While not all medical isotopes are radioactive, radiopharmaceuticals are the oldest, as with other pharmaceutical drugs, there is standardization of the drug nomenclature for radiopharmaceuticals, although various standards coexist. The International Nonproprietary Names, United States Pharmacopeia names, and IUPAC names for these agents are usually similar other than trivial style differences, the details are explained at Radiopharmacology § Drug nomenclature for radiopharmaceuticals. A list of nuclear medicine radiopharmaceuticals follows, some radioisotopes* are used in ionic or inert form without attachment to a pharmaceutical, these are also included. There is a section for each radioisotope with a table of radiopharmaceuticals using that radioisotope, the sections are ordered alphabetically by the English name of the radioisotope. Sections for the element are then ordered by atomic mass number. 47Ca is a beta and gamma emitter, 18F is a positron emitter with a half life of 109 minutes. It is produced in cyclotrons, usually from oxygen-18. 68Ga is an emitter, with a 68-minute half life. 3H or tritium is a beta emitter and it is used only diagnostically, as its radiation is penetrating and short-lived. 125I is an emitter with a long half-life of 59.4 days. I-125s gamma radiation is of medium penetration, making it useful as a therapeutic isotope for brachytherapy implant of radioisotope capsules for local treatment of cancers. 131I is a beta and gamma emitter and it is used both to destroy thyroid and thyroid cancer tissues, and also other neuroendocrine tissues when used in MIBG. It can also be seen by a camera, and can serve as a diagnostic imaging tracer. However iodine-123 is usually preferred when only imaging is desired, 59Fe is a beta and gamma emitter. 82Rb is a positron and gamma emitter, 153Sm is a beta and gamma emitter
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Environmental radioactivity
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Environmental radioactivity is produced by radioactive materials in the human environment. g. Tritium, result from natural processes and human activities. The concentration and location of natural isotopes, particularly uranium-238. Radioactivity is present everywhere, and has been since the formation of the earth, according to the IAEA, soil typically contains the following four natural radioisotopes, 40K, 226Ra, 238U, and 232Th. In one kilogram of soil, the amounts to an average 370 Bq of radiation, with a typical range of 100–700 Bq. Some soils may vary greatly from these norms, a recent report on the Sava river in Serbia suggests that many of the river silts contain about 100 Bq kg−1 of natural radioisotopes. According to the United Nations the normal concentration of uranium in soil ranges between 300 μg kg−1 and 11.7 mg kg−1, synthetic radioisotopes also can be detected in silt. Some relationship between distance and activity can be seen in their data, when fitted to an exponential curve, normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials. For instance the release of 99Tc from a nuclear medicine department of a hospital which occurs when a given a Tc imaging agent expels the agent. Releases of man-made radioactive materials which occur during an industrial or research accident, releases which occur as a result of military activity. For example, a weapons test. Releases which occur as a result of a crime, for example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation. Releases of naturally occurring radioactive materials as a result of mining etc, for example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations. Just because a radioisotope lands on the surface of the soil, after release into the environment, radioactive materials can reach humans in a range of different routes, and the chemistry of the element usually dictates the most likely route. Using milk as an example, if the cow has an intake of 1000 Bq of the preceding isotopes then the milk will have the following activities. 90Sr,2 Bq dm−3 137Cs,5 Bq dm−3 239Pu,0.001 Bq dm−3 241Am,0, the distribution coefficient Kd is the ratio of the soils radioactivity to that of the soil water. If the radioactivity is tightly bonded to by the minerals in the then less radioactivity can be absorbed by crops. Cs-137 Kd =1000 Pu-239 Kd =10000 to 100000 Sr-90 Kd =80 to 150 I-131 Kd =0.007 to 50 One dramatic source of radioactivity is a nuclear weapons test
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Stellar nucleosynthesis
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Stellar nucleosynthesis is the process by which the natural abundances of the chemical elements within stars change due to nuclear fusion reactions in the cores and their overlying mantles. Stars are said to evolve with changes in the abundances of the elements within, a star loses most of its mass when it is ejected late in the stars stellar lifetimes, thereby increasing the abundance of elements heavier than helium in the interstellar medium. The term supernova nucleosynthesis is used to describe the creation of elements during the evolution and explosion of a presupernova star, a stimulus to the development of the theory of nucleosynthesis was the discovery of variations in the abundances of elements found in the universe. Those abundances, when plotted on a graph as a function of number of the element, have a jagged sawtooth shape that varies by factors of tens of millions. This suggested a natural process other than random, such a graph of the abundances can be seen at History of nucleosynthesis theory article. Of the several processes of nucleosynthesis, stellar nucleosynthesis is the contributor to elemental abundances in the universe. The fusion of nuclei in a star, starting from its initial hydrogen and helium abundance, provides it energy and this became clear during the decade prior to World War II. The fusion-produced nuclei are restricted to only slightly heavier than the fusing nuclei. Nonetheless, this raised the plausibility of explaining all of the natural abundances of elements in this way. The prime energy producer in our Sun is the fusion of hydrogen to form helium, in 1920, Arthur Eddington, on the basis of the precise measurements of atomic masses by F. W. This was a step toward the idea of nucleosynthesis. In 1939, in a paper entitled Energy Production in Stars and he defined two processes that he believed to be the sources of energy in stars. The first one, the chain reaction, is the dominant energy source in stars with masses up to about the mass of the Sun. The second process, the cycle, which was also considered by Carl Friedrich von Weizsäcker in 1938, is most important in more massive stars. These works concerned the energy capable of keeping stars hot. A clear physical description of the chain and of the CNO cycle appears in a 1968 textbook. Bethes two papers did not address the creation of heavier nuclei, however and that theory was begun by Fred Hoyle in 1946 with his argument that a collection of very hot nuclei would assemble into iron. Hoyle followed that in 1954 with a paper describing how advanced fusion stages within stars would synthesize elements between carbon and iron in mass
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Supernova
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This causes the sudden appearance of a new bright star, before slowly fading from sight over several weeks or months. Supernovae are more energetic than novae, in Latin, nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, only three Milky Way naked-eye supernova events have been observed during the last thousand years, though many have been seen in other galaxies using telescopes. The most recent directly observed supernova in the Milky Way was Keplers Supernova in 1604, Supernovae may expel much, if not all, of the material away from a star, at velocities up to 30,000 km/s or 10% of the speed of light. This drives an expanding and fast-moving shock wave into the interstellar medium, and in turn, sweeping up an expanding shell of gas and dust. Supernovae create, fuse and eject the bulk of the chemical elements produced by nucleosynthesis, Supernovae play a significant role in enriching the interstellar medium with the heavier atomic mass chemical elements. Furthermore, the shock waves from supernovae can trigger the formation of new stars. Supernova remnants are expected to accelerate a large fraction of primary cosmic rays. They are also potentially strong galactic sources of gravitational waves, in the second case, the core of a massive star may undergo sudden gravitational collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical collapse mechanics have been established and accepted by most astronomers for some time, in Latin, Nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, the earliest recorded supernova, SN185, was viewed by Chinese astronomers in 185 AD. The brightest recorded supernova was SN1006, which occurred in 1006 AD and was described in detail by Chinese, the widely observed supernova SN1054 produced the Crab Nebula. Johannes Kepler began observing SN1604 at its peak on October 17,1604 and it was the second supernova to be observed in a generation. There is some evidence that the youngest galactic supernova, G1. 9+0.3, occurred in the late 19th century, neither supernova was noted at the time. In the case of G1. 9+0.3, high extinction along the plane of the galaxy could have dimmed the event sufficiently to go unnoticed, the situation for Cassiopeia A is less clear. Infrared light echos have been detected showing that it was a type IIb supernova and was not in a region of especially high extinction, before the development of the telescope, there have only been five supernovae seen in the last millennium
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Uranium
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Uranium is a chemical element with symbol U and atomic number 92. It is a metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons, Uranium is weakly radioactive because all its isotopes are unstable. The most common isotopes in natural uranium are uranium-238 and uranium-235, Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and it occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium is found as uranium-238, uranium-235, Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years, many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the naturally occurring fissile isotope, which makes it widely used in nuclear power plants. However, because of the amounts found in nature, uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor, another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. In sufficient concentration, these maintain a sustained nuclear chain reaction. This generates the heat in nuclear reactors, and produces the fissile material for nuclear weapons. Depleted uranium is used in kinetic energy penetrators and armor plating, Uranium is used as a colorant in uranium glass, producing lemon yellow to green colors. Uranium glass fluoresces green in ultraviolet light and it was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Henri Becquerel. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of weapons that used uranium metal. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is a concern for public health. When refined, uranium is a white, weakly radioactive metal
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Thorium
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Thorium is a chemical element with symbol Th and atomic number 90. A radioactive actinide metal, thorium is one of only two significantly radioactive elements that occur naturally in large quantities as a primordial element. It was discovered in 1829 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, a thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons. Thorium metal is silvery and tarnishes black when exposed to air, Thorium is weakly radioactive, all of its known isotopes are unstable. Thorium-232, which has 142 neutrons, is the most stable isotope of thorium and accounts for all natural thorium. Thorium is estimated to be three to four times more abundant than uranium in the Earths crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals. Thorium was once used as the light source in gas mantles and as an alloying material. Thorium is still used as an alloying element in TIG welding electrodes. Thorium is predicted to be able to replace uranium as fuel in nuclear reactors. Thorium is a soft, paramagnetic, bright silvery radioactive actinide metal, in the periodic table, it is located to the right of the actinide actinium, to the left of the actinide protactinium, and below the lanthanide cerium. Pure thorium is very ductile and, as normal for metals, can be cold-rolled, swaged, at room temperature, thorium metal has a face-centred cubic crystal structure, additionally, it has two other forms at exotic conditions, one at high temperature and one at high pressure. The properties of thorium vary widely depending on the amount of impurities in the sample, the purest thorium specimens usually contain about a tenth of a percent of the dioxide. These values lie intermediate between those of its neighbours actinium and protactinium, showing the continuity of trends across the early actinides, thoriums melting point of 1750 °C is above both that of actinium and that of protactinium. After thorium, there is a new smooth trend downward in the points of the early actinides from thorium to plutonium where the number of f electrons increases from about 0. Thorium has a modulus of 54 GPa, comparable to those of tin. The hardness of thorium is similar to that of steel, so heated pure thorium can be rolled in sheets. Nevertheless, while thorium is nearly half as dense as uranium and plutonium, Thorium becomes superconductive below 1.4 K. Thorium can also form alloys with many other metals. With chromium and uranium, it forms eutectic mixtures, and thorium is completely miscible in both solid and liquid states with its lighter congener cerium, as such, 232Th still occurs naturally today, four-fifths of the thorium present at Earths formation has survived to the present
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Bismuth
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Bismuth is a chemical element with the symbol Bi and atomic number 83. Bismuth, a pentavalent post-transition metal and one of the pnictogens, chemically resembles its lighter homologs arsenic, elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead and it is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. Bismuth is the most naturally diamagnetic element, and has one of the lowest values of thermal conductivity among metals, Bismuth metal has been known since ancient times, although it was often confused with lead and tin, which share some physical properties. Bismuth was long considered the element with the highest atomic mass that is stable, because of its tremendously long half-life, bismuth may still be considered stable for almost all purposes. Bismuth compounds account for half the production of bismuth. They are used in cosmetics, pigments, and a few pharmaceuticals, notably bismuth subsalicylate, bismuths unusual propensity to expand upon freezing is responsible for some of its uses, such as in casting of printing type. Bismuth has unusually low toxicity for a heavy metal, as the toxicity of lead has become more apparent in recent years, there is an increasing use of bismuth alloys as a replacement for lead. The name bismuth dates from around the 1660s, and is of uncertain etymology and it is one of the first 10 metals to have been discovered. Bismuth appears in the 1660s, from obsolete German Bismuth, Wismut, Wissmuth, the New Latin bisemutum is from the German Wismuth, perhaps from weiße Masse, white mass. The element was confused in early times with tin and lead because of its resemblance to those elements, Bismuth has been known since ancient times, so no one person is credited with its discovery. Agricola, in De Natura Fossilium states that bismuth is a metal in a family of metals including tin. This was based on observation of the metals and their physical properties, miners in the age of alchemy also gave bismuth the name tectum argenti, or silver being made, in the sense of silver still in the process of being formed within the Earth. Bismuth was also known to the Incas and used in a bronze alloy for knives. Bismuth is a metal with a white, silver-pink hue, often occurring in its native form. The spiral, stair-stepped structure of crystals is the result of a higher growth rate around the outside edges than on the inside edges. The variations in the thickness of the layer that forms on the surface of the crystal causes different wavelengths of light to interfere upon reflection. When burned in oxygen, bismuth burns with a blue flame and its toxicity is much lower than that of its neighbors in the periodic table, such as lead, antimony, and polonium
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Decay chain
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In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations. They are also known as radioactive cascades, most radioisotopes do not decay directly to a stable state, but rather undergo a series of decays until eventually a stable isotope is reached. Decay stages are referred to by their relationship to previous or subsequent stages, a parent isotope is one that undergoes decay to form a daughter isotope. One example of this is uranium decaying into thorium, the daughter isotope may be stable or it may decay to form a daughter isotope of its own. The daughter of an isotope is sometimes called a granddaughter isotope. Half-lives have been determined in laboratories for thousands of radioisotopes and these can range from nearly instantaneous to as much as 1019 years or more. The intermediate stages each emit the same amount of radioactivity as the original radioisotope, not only are unstable radium isotopes significant radioactivity emitters, but as the next stage in the decay chain they also generate radon, a heavy, inert, naturally occurring radioactive gas. Rock containing thorium and/or uranium emits radon gas that can accumulate in enclosed places such as basements or underground mines, radon exposure is considered the leading cause of lung cancer in non-smokers.5 billion years ago. All the elements created more than 4.5 billion years ago are termed primordial, at the time when they were created, those that were unstable began decaying immediately. There are only two methods to create isotopes, artificially, inside a man-made reactor, or through decay of a parent isotopic species. Unstable isotopes are in a struggle to become more stable. Stable isotopes have ratios of neutrons to protons in their nucleus that start out at 1 in stable helium-4, the elements heavier than that have to shed weight to achieve stability, most usually as alpha decay. This fact is made inevitable by the two decay methods possible, alpha radiation, which reduces the weight by 4 atomic mass units, and beta, which does not change the weight at all. The four paths are termed 4n, 4n +1, 4n +2, and 4n +3, there are other decay modes, but they invariably occur at a lower probability than alpha or beta decay. Three of those chains have a long-lived isotope near the top, they are bottlenecks in the process through which the chain flows very slowly, the three materials are uranium-238, uranium-235 and thorium-232. The fourth chain has no long lasting bottleneck isotope, so almost all of the isotopes in that chain have long since decayed down to very near the stability at the bottom. Near the end of that chain is bismuth-209, which was thought to be stable. Recently, however, Bi-209 was found to be unstable with a half-life of 19 billion billion years, the four most common modes of radioactive decay are, alpha decay, beta decay, inverse beta decay, and isomeric transition
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Polonium
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Polonium is a chemical element with symbol Po and atomic number 84. Though slightly longer-lived isotopes exist, they are more difficult to produce. Today, polonium is usually produced in quantities by the neutron irradiation of bismuth. Due to its radioactivity, which results in the radiolysis of chemical bonds and radioactive self-heating. Polonium was discovered in 1898 by Marie and Pierre Curie, when it was extracted from ore and identified solely by its strong radioactivity. Polonium was named after Marie Curies homeland of Poland, Polonium has few applications, and those are related to its radioactivity, heaters in space probes, antistatic devices, and sources of neutrons and alpha particles. Poloniums intense radioactivity makes it dangerously toxic, Polonium has 33 known isotopes, all of which are radioactive. They have atomic masses that range from 188 to 220 u. 210Po is the most widely available, the longer-lived 209Po and 208Po can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron. 210Po is an alpha emitter that has a half-life of 138.4 days, it directly to its stable daughter isotope. A milligram of 210Po emits about as many alpha particles per second as 5 grams of 226Ra, a few curies of 210Po emit a blue glow which is caused by ionisation of the surrounding air. About one in 100,000 alpha emissions causes an excitation in the nucleus which results in the emission of a gamma ray with a maximum energy of 803 keV. Polonium is an element that exists in two metallic allotropes. The alpha form is the known example of a simple cubic crystal structure in a single atom basis, with an edge length of 335.2 picometers. The structure of polonium has been characterized by X-ray diffraction and electron diffraction, more than one hypothesis exists for how polonium does this, one suggestion is that small clusters of polonium atoms are spalled off by the alpha decay. The chemistry of polonium is similar to that of tellurium, although it shows some similarities to its neighbor bismuth due to its metallic character. Polonium dissolves readily in dilute acids but is slightly soluble in alkalis. Polonium solutions are first colored in pink by the Po2+ ions, Polonium has no common compounds, and almost all of its compounds are synthetically created, more than 50 of those are known. The most stable class of compounds are polonides, which are prepared by direct reaction of two elements
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Radium
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Radium is a chemical element with symbol Ra and atomic number 88. It is the element in group 2 of the periodic table. Pure radium is silvery-white, but it combines with nitrogen on exposure to air. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, when radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence. Radium, in the form of chloride, was discovered by Marie. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later, Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911. In nature, radium is found in uranium and thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and adverse effects are likely when it is incorporated into biochemical processes because of its radioactivity. Today, these applications are no longer in vogue because radiums toxicity has since become known. Radium is the heaviest known alkaline earth metal and is the only member of its group. Its physical and chemical properties most closely resemble its lighter congener barium, pure radium is a volatile silvery-white metal, although its lighter congeners calcium, strontium, and barium have a slight yellow tint. Its color rapidly vanishes in air, yielding a layer of radium nitride. Its melting point is either 700 °C or 960 °C and its point is 1,737 °C. Both of these values are lower than those of barium. Like barium and the metals, radium crystallizes in the body-centered cubic structure at standard temperature and pressure. Radium has a density of 5, Radium, like barium, is a highly reactive metal and always exhibits its group oxidation state of +2. It forms the colorless Ra2+ cation in aqueous solution, which is highly basic, the values for barium and radium are almost exactly the same as those of the heavier alkali metals potassium, rubidium, and caesium. Solid radium compounds are white as radium ions provide no specific coloring, insoluble radium compounds coprecipitate with all barium, most strontium, and most lead compounds
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Cosmogenic isotopes
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Environmental radioactivity is produced by radioactive materials in the human environment. g. Tritium, result from natural processes and human activities. The concentration and location of natural isotopes, particularly uranium-238. Radioactivity is present everywhere, and has been since the formation of the earth, according to the IAEA, soil typically contains the following four natural radioisotopes, 40K, 226Ra, 238U, and 232Th. In one kilogram of soil, the amounts to an average 370 Bq of radiation, with a typical range of 100–700 Bq. Some soils may vary greatly from these norms, a recent report on the Sava river in Serbia suggests that many of the river silts contain about 100 Bq kg−1 of natural radioisotopes. According to the United Nations the normal concentration of uranium in soil ranges between 300 μg kg−1 and 11.7 mg kg−1, synthetic radioisotopes also can be detected in silt. Some relationship between distance and activity can be seen in their data, when fitted to an exponential curve, normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials. For instance the release of 99Tc from a nuclear medicine department of a hospital which occurs when a given a Tc imaging agent expels the agent. Releases of man-made radioactive materials which occur during an industrial or research accident, releases which occur as a result of military activity. For example, a weapons test. Releases which occur as a result of a crime, for example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation. Releases of naturally occurring radioactive materials as a result of mining etc, for example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations. Just because a radioisotope lands on the surface of the soil, after release into the environment, radioactive materials can reach humans in a range of different routes, and the chemistry of the element usually dictates the most likely route. Using milk as an example, if the cow has an intake of 1000 Bq of the preceding isotopes then the milk will have the following activities. 90Sr,2 Bq dm−3 137Cs,5 Bq dm−3 239Pu,0.001 Bq dm−3 241Am,0, the distribution coefficient Kd is the ratio of the soils radioactivity to that of the soil water. If the radioactivity is tightly bonded to by the minerals in the then less radioactivity can be absorbed by crops. Cs-137 Kd =1000 Pu-239 Kd =10000 to 100000 Sr-90 Kd =80 to 150 I-131 Kd =0.007 to 50 One dramatic source of radioactivity is a nuclear weapons test
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Carbon-14
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Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby, Carbon-14 was discovered on 27 February 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934, carbon-12 and carbon-13 are both stable, while the half-life of carbon-14 is 5, 730±40 years. Carbon-14 decays into nitrogen-14 through beta decay, a gram of carbon containing 1 atom of carbon-14 per 1012 atoms will emit 0.40 beta particles per second. The primary natural source of carbon-14 on Earth is cosmic ray action on nitrogen in the atmosphere, however, open-air nuclear testing between 1955–1980 contributed to this pool. The different isotopes of carbon do not differ appreciably in their chemical properties, the emitted beta particles have a maximum energy of 156 keV, while their weighted mean energy is 49 keV. These are relatively low energies, the distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue. The fraction of the radiation transmitted through the dead layer is estimated to be 0.11. Liquid scintillation counting is the preferred method, the G-M counting efficiency is estimated to be 3%. The half-distance layer in water is 0.05 mm. Radiocarbon dating is a dating method that uses to determine the age of carbonaceous materials up to about 60,000 years old. The technique was developed by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago, in 1960, Libby was awarded the Nobel Prize in chemistry for this work. One of the frequent uses of the technique is to date organic remains from archaeological sites, plants fix atmospheric carbon during photosynthesis, so the level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time. However, it decreases thereafter from radioactive decay, allowing the date of death or fixation to be estimated. A calculation or a comparison of carbon-14 levels in a sample, with tree ring or cave-deposit carbon-14 levels of a known age. Carbon-14 is produced in the layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, the resulting neutrons participate in the following reaction, n +14 7N →14 6C + p The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km and at high geomagnetic latitudes. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation, the latter can create significant variations in 14C production rates, although the changes of the carbon cycle can make these effects difficult to tease out. Another extraordinarily large 14C increase has been associated with the 5480 BC event
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Cosmic ray
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Cosmic rays are high-energy radiation, mainly originating outside the Solar System. Upon impact with the Earths atmosphere, cosmic rays can produce showers of particles that sometimes reach the surface. Composed primarily of protons and atomic nuclei, they are of mysterious origin. Data from the Fermi space telescope have been interpreted as evidence that a significant fraction of cosmic rays originate from the supernovae explosions of stars. Active galactic nuclei probably also produce cosmic rays, the term ray is a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In current usage, the cosmic ray almost exclusively refers to massive particles. Massive particles – those that have rest mass – can gain additional, kinetic, mass-energy when they are moving, through this process, some particles acquire tremendously high mass-energies. These are significantly higher than the energy of even the highest-energy photons detected to date. The energy of the massless photon depends solely on frequency, not speed, at the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays. Hence, the highest-energy detected fermionic cosmic ray was around 3×106 times more energetic than the highest-energy detected cosmic photons, of primary cosmic rays, which originate outside of Earths atmosphere, about 99% are the nuclei of well-known atoms, and about 1% are solitary electrons. Of the nuclei, about 90% are simple protons, i. e. hydrogen nuclei, 9% are alpha particles, identical to helium nuclei, a very small fraction are stable particles of antimatter, such as positrons or antiprotons. The precise nature of this fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them, one can show that such enormous energies might be achieved by means of the Centrifugal mechanism of acceleration in Active galactic nuclei. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the energy of a 90-kilometre-per-hour baseball. As a result of discoveries, there has been interest in investigating cosmic rays of even greater energies. Most cosmic rays, however, do not have such extreme energies, however, his paper published in Physikalische Zeitschrift was not widely accepted. In 1911 Domenico Pacini observed simultaneous variations of the rate of ionization over a lake, over the sea, Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth. In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers to an altitude of 5300 meters in a balloon flight
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Nuclear fission
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In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts. The fission process often produces free neutrons and gamma photons, Frisch named the process by analogy with biological fission of living cells. It is a reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments. In order for fission to produce energy, the binding energy of the resulting elements must be less negative than that of the starting element. Fission is a form of nuclear transmutation because the fragments are not the same element as the original atom. The two nuclei produced are most often of comparable but slightly different sizes, typically with a ratio of products of about 3 to 2. Most fissions are binary fissions, but occasionally, three positively charged fragments are produced, in a ternary fission, the smallest of these fragments in ternary processes ranges in size from a proton to an argon nucleus. Nuclear fission produces energy for power and drives the explosion of nuclear weapons. Both uses are possible because certain substances called nuclear fuels undergo fission when struck by fission neutrons and this makes possible a self-sustaining nuclear chain reaction that releases energy at a controlled rate in a nuclear reactor or at a very rapid uncontrolled rate in a nuclear weapon. Nuclear fission can occur without neutron bombardment as a type of radioactive decay and this type of fission is rare except in a few heavy isotopes. In engineered nuclear devices, essentially all nuclear fission occurs as a nuclear reaction — a bombardment-driven process that results from the collision of two subatomic particles, in nuclear reactions, a subatomic particle collides with an atomic nucleus and causes changes to it. Nuclear reactions are driven by the mechanics of bombardment, not by the relatively constant exponential decay. Many types of reactions are currently known. Nuclear fission differs importantly from other types of reactions, in that it can be amplified. In such a reaction, free neutrons released by each fission event can trigger yet more events, the chemical element isotopes that can sustain a fission chain reaction are called nuclear fuels, and are said to be fissile. The most common nuclear fuels are 235U and 239Pu and these fuels break apart into a bimodal range of chemical elements with atomic masses centering near 95 and 135 u. Most nuclear fuels undergo spontaneous fission only very slowly, decaying instead mainly via an alpha-beta decay chain over periods of millennia to eons. In a nuclear reactor or nuclear weapon, the majority of fission events are induced by bombardment with another particle, a neutron
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Thermonuclear weapon
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A thermonuclear weapon is a nuclear weapon that uses the energy from a primary nuclear fission reaction to compress and ignite a secondary nuclear fusion reaction. The result is greatly increased power when compared to single-stage fission weapons. It is colloquially referred to as a bomb or an H-bomb because it employs the fusion of isotopes of hydrogen. The first full scale thermonuclear test was carried out by the United States in 1952, similar devices were developed by the Soviet Union, United Kingdom, China, and France. The radiation implosion mechanism is an engine that exploits the temperature difference between the secondary stages hot, surrounding radiation channel and its relatively cool interior. This temperature difference is maintained by a massive heat barrier called the pusher. If made of uranium, as is almost always the case, it can capture neutrons produced by the reaction and undergo fission itself. In many Teller–Ulam weapons, fission of the pusher dominates the explosion, detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized nation. Born secret is rarely invoked for cases of private speculation, in a small number of prior cases, the U. S. government has attempted to censor weapons information in the public press, with limited success. According to the New York Times, physicist Kenneth Ford defied government orders to remove classified information from his new book, Building the H Bomb, the state of public knowledge about the Teller–Ulam design has been mostly shaped from a few specific incidents outlined in a section below. At a bare minimum, this implies a primary section consists of an implosion-type fission bomb. The energy released by the primary compresses the secondary through a process called radiation implosion, at which point it is heated, surrounding the other components is a hohlraum or radiation case, a container that traps the first stage or primarys energy inside temporarily. The outside of this case, which is also normally the outside casing of the bomb, is the only direct visual evidence publicly available of any thermonuclear bomb components configuration. Numerous photographs of various thermonuclear bomb exteriors have been declassified, generally, a research program with the capacity to create a thermonuclear bomb has already mastered the ability to engineer boosted fission. The secondary is usually shown as a column of fusion fuel, around the column is first a pusher-tamper, a heavy layer of uranium-238 or lead that serves to help compress the fusion fuel. Inside this is the fuel itself, usually a form of lithium deuteride. This dry fuel, when bombarded by neutrons, produces tritium, inside the layer of fuel is the spark plug, a hollow column of fissile material that, when compressed, can itself undergo nuclear fission. The tertiary, if one is present, would be set below the secondary, separating the secondary from the primary is the interstage
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Nuclear fission product
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Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release of heat energy. The two smaller nuclei are the fission products, about 0. 2% to 0. 4% of fissions are ternary fissions, producing a third light nucleus such as helium-4 or tritium. The fission products themselves are often unstable and radioactive, due to being relatively neutron-rich for their atomic number and this releases additional energy in the form of beta particles, antineutrinos, and gamma rays. Thus, fission events normally result in radiation and antineutrinos. Many of these nuclides have a very short half-life, and therefore are very radioactive, for instance, strontium-90, strontium-89 and strontium-94 are all fission products, they are produced in similar quantities, and each nucleus decays by shooting off one beta particle. But Sr-90 has a 30-year half-life, Sr-89 a 50. 5-day half-life, the same number of atoms of Sr-89 will decay 10,600 times faster than Sr-90, and Sr-94 will do so 915 million times faster. It is these short-half-life nuclides that make spent fuel so dangerous, in addition to generating much heat, immediately after the reactor itself has been shut down. The most radioactive also decay the fastest, after 50 days, Sr-94 has had 58,000 half-lives and is gone, Sr-89 is at half its original quantity. As there are hundreds of different nuclides created, the radioactivity level fades quickly. The sum of the mass of the two atoms produced by the fission of one fissile atom is always less than the atomic mass of the original atom. Since the nuclei that can undergo fission are particularly neutron-rich. The initial fission products therefore may be unstable and typically undergo beta decay to move towards a stable configuration, a few neutron-rich and short-lived initial fission products decay by ordinary beta decay, followed by immediate emission of a neutron by the excited daughter-product. This process is the source of so-called delayed neutrons, which play an important role in control of a nuclear reactor, the first beta decays are rapid and may release high energy beta particles or gamma radiation. However, as the fission products approach stable nuclear conditions, the last one or two decays may have a long half-life and release less energy. Fission products have half-lives of 90 years or less, except for seven long-lived fission products that have lives of 211,100 years. This behavior of pure fission products with actinides removed, contrasts with the decay of fuel that still contains actinides and this fuel is produced in the so-called open nuclear fuel cycle. A number of these actinides have half lives in the range of about 100 to 200,000 years
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Actinide
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The actinide /ˈæktᵻnaɪd/ or actinoid /ˈæktᵻnɔɪd/ series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, the informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell, lawrencium, in comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. They all have very large atomic and ionic radii and exhibit a large range of physical properties. While actinium and the late actinides behave similarly to the lanthanides, all actinides are radioactive and release energy upon radioactive decay, naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons, uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors. Of the actinides, primordial thorium and uranium occur naturally in substantial quantities, the radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements, like the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups, transuranium elements, which follow uranium in the periodic table—and transplutonium elements, compared to the lanthanides, which are found in nature in appreciable quantities, most actinides are rare. The most abundant, or easily synthesized actinides are uranium and thorium, the existence of transuranium elements was suggested by Enrico Fermi based on his experiments in 1934. However, even though four actinides were known by that time, synthesis of transuranics gradually undermined this point of view. By 1944 an observation that curium failed to exhibit oxidation states above 4 prompted Glenn Seaborg to formulate a so-called actinide hypothesis, at present, there are two major methods of producing isotopes of transplutonium elements, irradiation of the lighter elements with either neutrons or accelerated charged particles. The advantage of the method is that elements heavier than plutonium, as well as neutron-deficient isotopes, can be obtained. In 1962–1966, there were attempts in the United States to produce transplutonium isotopes using a series of six underground nuclear explosions and this inobservation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission. Uranium and thorium were the first actinides discovered, uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus, which had been discovered eight years earlier. Klaproth was able to precipitate a yellow compound by dissolving pitchblende in nitric acid and he then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal. Only 60 years later, the French scientist Eugène-Melchior Péligot identified it with uranium oxide and he also isolated the first sample of uranium metal by heating uranium tetrachloride with potassium
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Radioactive waste
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Radioactive waste is waste that contains radioactive material. Radioactive waste is usually a by-product of nuclear generation and other applications of nuclear fission or nuclear technology, such as research. Radioactive waste is hazardous to most forms of life and the environment, and is regulated by government agencies in order to protect human health and the environment. Radioactivity naturally decays over time, so radioactive waste has to be isolated and confined in appropriate facilities for a sufficient period until it no longer poses a threat. The time radioactive waste must be stored for depends on the type of waste, Radioactive waste typically comprises a number of radionuclides, unstable configurations of elements that decay, emitting ionizing radiation which can be harmful to humans and the environment. These isotopes emit different types and levels of radiation, which last for different periods of time, the radioactivity of all radioactive waste diminishes with time. Certain radioactive elements will remain hazardous to humans and other creatures for hundreds or thousands of years, other radionuclides remain radioactive for millions of years. Thus, these wastes must be shielded for centuries and isolated from the environment for millennia. Since radioactive decay follows the rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be less intense than that of a short-lived isotope like iodine-131. The two tables show some of the radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235. The energy and the type of the radiation emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the element will determine how mobile the substance is and how likely it is to spread into the environment. Exposure to radioactive waste may cause harm or death. In humans, a dose of 1 sievert carries a 5. 5% risk of developing cancer, ionizing radiation causes deletions in chromosomes. If a developing organism such as a child is irradiated, it is possible a birth defect may be induced. The incidence of radiation-induced mutations in humans is small, as in most mammals, because of natural cellular-repair mechanisms, Radioactive waste comes from a number of sources. Waste from the front end of the fuel cycle is usually alpha-emitting waste from the extraction of uranium
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Nuclear fallout
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It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes, but such dust can also originate from a damaged nuclear plant. Fallout may get entrained with the products of a pyrocumulus cloud and this radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron activated by exposure, is a highly dangerous kind of radioactive contamination. An air burst can eventually produce worldwide fallout, a ground burst can produce possibly much more severe, local fallout. These particles may be drawn up into the stratosphere, particularly if the explosive yield exceeds 10 kt. Initially little was known about the dispersion of nuclear fallout on a global scale, the AEC assumed that fallout would be dispersed evenly across the globe by atmospheric winds and gradually settle to the Earths surface after weeks, months, and even years as worldwide fallout. This hazard is less pertinent than local fallout, which is of much greater immediate operational concern, in a land or water surface burst, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it condenses with fission products and other radiocontaminants that have become neutron-activated, the table below summarizes the abilities of common isotopes to form fallout. Some radiation taints large amounts of land and drinking water causing formal mutations throughout animal and human life. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, more than half the total bomb debris lands on the ground within about 24 hours as local fallout. Chemical properties of the elements in the control the rate at which they are deposited on the ground. Severe local fallout contamination can extend far beyond the blast and thermal effects, the ground track of fallout from an explosion depends on the weather from the time of detonation onwards. In stronger winds, fallout travels faster but takes the time to descend, so although it covers a larger path. Thus, the width of the pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any time is the same irrespective of the wind pattern. But thunderstorms can bring down activity as rain more rapidly than dry fallout, particularly if the cloud is low enough to be below, or mixed with. There are two considerations for the location of an explosion, height and surface composition. A nuclear weapon detonated in the air, called an air burst, in case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water, these can have a cloud seeding effect causing local rainout and areas of high local fallout
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Nuclide
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A nuclide is an atomic species characterized by the specific constitution of its nucleus, i. e. by its number of protons Z, its number of neutrons N, and its nuclear energy state. The word nuclide was proposed by Truman P. Kohman in 1947, Kohman originally suggested nuclide as referring to a species of nucleus defined by containing a certain number of neutrons and protons. The word thus was originally intended to focus on the nucleus, nuclide refers to a nucleus rather than to an atom. Identical nuclei belong to one nuclide, for each nucleus of the carbon-13 nuclide is composed of 6 protons and 7 neutrons. The nuclide concept emphasizes nuclear properties over chemical properties, while the isotope concept emphasizes chemical over nuclear, the neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. Since isotope is the term, it is better known than nuclide. A set of nuclides with equal number, i. e. of the same chemical element but different neutron numbers, are called isotopes of the element. Particular nuclides are still often loosely called isotopes, but the term nuclide is the one in general. In similar manner, a set of nuclides with equal mass number A, but different atomic number, are called isobars, and isotones are nuclides of equal neutron number but different proton numbers. The name isotone has been derived from the isotope to emphasize that in the first group of nuclides it is the number of neutrons that is constant. See Isotope#Notation for an explanation of the used for different nuclide or isotope types. Nuclear isomers are members of a set of nuclides with equal number and equal mass number. An example is the two states of the single isotope 99 43Tc shown among the decay schemes, each of these two states qualifies as a different nuclide, illustrating one way that nuclides may differ from isotopes. The most long-lived non-ground state nuclear isomer is the nuclide tantalum-180m and this nuclide occurs primordially, and has never been observed to decay to the ground state. There are about 254 nuclides in nature that have never observed to decay. They occur among the 80 different elements that have one or more stable isotopes, see stable isotope and primordial nuclide. Unstable nuclides are radioactive and are called radionuclides and their decay products are called radiogenic nuclides. About 254 stable and about 85 unstable nuclides exist naturally on Earth, natural radionuclides may be conveniently subdivided into three types
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Americium-241
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Americium-241 is an isotope of americium. Like all isotopes of americium, it is radioactive, 241Am is the most common isotope of americium. It is the most prevalent isotope of americium in nuclear waste, americium-241 has a half-life of 432.2 years. It is commonly found in ionization smoke detectors. It is a fuel for long-lifetime radioisotope thermoelectric generators. Its common parent nuclides are β− from 241Pu, EC from 241Cm, 241Am is fissile and the critical mass of a bare sphere is 57. 6-75.6 kilograms and a sphere diameter of 19–21 centimeters. Americium-241 has an activity of 3.43 Ci/g. It is commonly found in the form of americium-241 dioxide and this isotope also has one meta state, 241mAm, with an exitation energy of 2.2 MeV, and a half-life of 1.23 μs. Its presence in plutonium is determined by the concentration of plutonium-241. Because of the low penetration of radiation, americium-241 only poses a health risk when ingested or inhaled. Older samples of plutonium containing plutonium-241 contain a buildup of 241Am, a chemical removal of americium-241 from reworked plutonium may be required in some cases. Americium-241 has been produced in quantities in nuclear reactors for decades. Nevertheless, since it was first offered for sale in 1962, its price, about 1,500 USD per gram of 241Am, americium-241 is not synthesized directly from uranium – the most common reactor material – but from the plutonium isotope 239Pu. Because it converts to 241Am, 241Pu can be extracted and may be used to generate further 241Am. However, this process is slow, half of the original amount of 241Pu decays to 241Am after about 14 years. The obtained 241Am can be used for generating heavier americium isotopes by further neutron capture inside a nuclear reactor. The γ-ray energy is 59.5409 keV for the most part, the second most common type of decay for americium-241 is cluster decay, with a branching ratio of less than 7. 4×10−16. This isotope is preferred over 226Ra as 241Am emits 5 times more alpha particles, some old industrial smoke detectors can contain up to 80 μCi
. Bibcode:2006RvMP...78..991S. doi:10.1103/RevModPhys.78.991.
