1.
Ruthenium
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Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a transition metal belonging to the platinum group of the periodic table. Like the other metals of the group, ruthenium is inert to most other chemicals. The Baltic German scientist Karl Ernst Claus discovered the element in 1844 and named it after his homeland, ruthenium is usually found as a minor component of platinum ores, the annual production is about 20 tonnes. Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors, a minor application for ruthenium is in platinum alloys and as a chemistry catalyst. This anomaly is observed in the metals, niobium, rhodium. Ruthenium has four crystal modifications and does not tarnish unless subject to high temperatures, ruthenium dissolves in fused alkalis to give ruthenates, is not attacked by acids but is attacked by halogens at high temperatures. Indeed, ruthenium is most readily attacked by oxidizing agents, small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is increased markedly by the addition of an amount of ruthenium. The metal can be plated by electroplating and by thermal decomposition, a ruthenium-molybdenum alloy is known to be superconductive at temperatures below 10.6 K. Like iron but unlike osmium, ruthenium can form aqueous cations in its lower oxidation states of +2, unlike the lighter congener iron, ruthenium is paramagnetic at room temperature, as iron also is above its Curie point. The reduction potentials in acidic aqueous solution for some common ruthenium ions are shown below, additionally,34 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are 106Ru with a half-life of 373.59 days, 103Ru with a half-life of 39.26 days, fifteen other radioisotopes have been characterized with atomic weights ranging from 89.93 u to 114.928 u. Most of these have half-lives that are less than five minutes except 95Ru and 105Ru, the primary decay mode before the most abundant isotope, 102Ru, is electron capture and the primary mode after is beta emission. The primary decay product before 102Ru is technetium and the decay product after is rhodium. As the 74th most abundant element in Earths crust, ruthenium is relatively rare and this element is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are found in pentlandite extracted from Sudbury, Ontario, Canada. The native form of ruthenium is a rare mineral
2.
Permalloy
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Permalloy is a nickel–iron magnetic alloy, with about 80% nickel and 20% iron content. Commercial permalloy alloys typically have relative permeability of around 100,000, in addition to high permeability, its other magnetic properties are low coercivity, near zero magnetostriction, and significant anisotropic magnetoresistance. Permalloys electrical resistivity can vary as much as 5% depending on the strength, permalloys typically have the face centered cubic crystal structure with a lattice constant of approximately 0.355 nm in the vicinity of a nickel concentration of 80%. Permalloy is used in transformer laminations and magnetic recording heads, Permalloy was initially developed in the early 20th century for inductive compensation of telegraph cables. The right conditions for transmitting signals through cables without distortion were first worked out mathematically in 1885 by Oliver Heaviside. It was proposed by Carl Emil Krarup in 1902 in Denmark that the cable could be compensated by wrapping it with wire, increasing the inductance. However, iron did not have high permeability to compensate a transatlantic-length cable. After a prolonged search, permalloy was discovered in 1914 by Gustav Elmen of Bell Laboratories, later, in 1923, he found its permeability could be greatly enhanced by heat treatment. A wrapping of permalloy tape could reportedly increase the speed of a telegraph cable fourfold. This method of cable compensation declined in the 1930s, but by World War 2 many other uses for Permalloy were found in the electronics industry, molybdenum permalloy is an alloy of 81% nickel, 17% iron and 2% molybdenum. The latter was invented at Bell Labs in 1940, at the time, when used in long distance copper telegraph lines, it allowed a tenfold increase in maximum line working speed. Supermalloy, at 79% Ni, 16% Fe, and 5% Mo, is well known for its high performance as a soft magnetic material, characterized by high permeability. Loading coil Mu-metal Sendust Supermalloy Richard M. Bozorth, Ferromagnetism, Wiley-IEEE Press, P. Ciureanu and S. Middelhoek, eds. Thin Film Resistive Sensors, Institute of Physics Publishing, ISBN 0-7503-0173-2
3.
Yttrium
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Yttrium is a chemical element with symbol Y and atomic number 39. It is a transition metal chemically similar to the lanthanides and has often been classified as a rare earth element. Yttrium is almost always found in combination with elements in rare earth minerals. 89Y is the stable isotope, and the only isotope found in the Earths crust. In 1787, Carl Axel Arrhenius found a new mineral near Ytterby in Sweden and named it ytterbite, johan Gadolin discovered yttriums oxide in Arrhenius sample in 1789, and Anders Gustaf Ekeberg named the new oxide yttria. Elemental yttrium was first isolated in 1828 by Friedrich Wöhler, the most important uses of yttrium are LEDs and phosphors, particularly the red phosphors in television set cathode ray tube displays. Yttrium has no biological role. Exposure to yttrium compounds can cause disease in humans. Yttrium is a soft, silver-metallic, lustrous and highly crystalline transition metal in group 3, yttrium is the first d-block element in the fifth period. The pure element is relatively stable in air in bulk form and this film can reach a thickness of 10 µm when yttrium is heated to 750 °C in water vapor. When finely divided, however, yttrium is very unstable in air, yttrium nitride is formed when the metal is heated to 1000 °C in nitrogen.5 to 67.5, placing it between the lanthanides gadolinium and erbium. It often also falls in the range for reaction order. Yttrium is so close in size to the yttrium group of heavy lanthanide ions that in solution. Even though the lanthanides are one row farther down the table than yttrium. As a trivalent transition metal, yttrium forms various inorganic compounds, generally in the state of +3. A good example is yttrium oxide, also known as yttria, yttrium forms a water-insoluble fluoride, hydroxide, and oxalate, but its bromide, chloride, iodide, nitrate and sulfate are all soluble in water. The Y3+ ion is colorless in solution because of the absence of electrons in the d and f electron shells, water readily reacts with yttrium and its compounds to form Y 2O3. Concentrated nitric and hydrofluoric acids do not rapidly attack yttrium, with halogens, yttrium forms trihalides such as yttrium fluoride, yttrium chloride, and yttrium bromide at temperatures above roughly 200 °C
4.
Silver
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Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, jewelry, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table, copper and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft, ductile and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm. The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper
5.
Gadolinium
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Gadolinium is a chemical element with symbol Gd and atomic number 64. Gadolinium is a silvery-white, malleable, and ductile rare earth metal and it is found in nature only in oxidized form, and even when separated, it usually has impurities of the other rare earths. Gadolinium was discovered in 1880 by Jean Charles de Marignac, who detected its oxide by using spectroscopy and it is named after the mineral gadolinite, which is one of the minerals in which gadolinium is found, itself named for the chemist Johan Gadolin. Pure gadolinium was first isolated by the chemist Paul Emile Lecoq de Boisbaudran in about 1886, Gadolinium as a metal or a salt absorbs neutrons, and it is, therefore, used sometimes for shielding in neutron radiography, and also in nuclear reactors. Like most of the rare earths, gadolinium forms trivalent ions with fluorescent properties, the kinds of gadolinium ions occurring in water-soluble salts are toxic to mammals. However, chelated gadolinium compounds are far less toxic because they carry gadolinium through the kidneys, Gadolinium is a silvery-white malleable and ductile rare earth metal. It crystallizes in hexagonal, in the close-packed α-form at room temperature, but, when heated to temperatures above 1235 °C, it transforms into its β-form, the isotope gadolinium-157 has the highest thermal neutron capture cross-section among any stable nuclide, about 259,000 barns. Only xenon-135 has a capture cross section, about 2.0 million barns. Gadolinium is believed to be ferromagnetic at temperatures below 20 °C, there is evidence that gadolinium is a helical antiferromagnetic, rather than a ferromagnetic, below 20 °C. Gadolinium demonstrates a magnetocaloric effect whereby its temperature increases when it enters a magnetic field, the temperature is lowered to 5 °C for the gadolinium alloy Gd85Er15, and this effect is considerably stronger for the alloy Gd5, but at a much lower temperature. A significant magnetocaloric effect is observed at higher temperatures, up to about 300 kelvin, in the compounds Gd54, individual gadolinium atoms can be isolated by encapsulating them into fullerene molecules, where they can be visualized with transmission electron microscope. Individual Gd atoms and small Gd clusters can be incorporated into carbon nanotubes, Gadolinium combines with most elements to form Gd derivatives. It also combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon, unlike the other rare earth elements, metallic gadolinium is relatively stable in dry air. However, it quickly in moist air, forming a loosely-adhering gadolinium oxide. 4 Gd +3 O2 →2 Gd2O3 Gadolinium is a reducing agent. All are white except for the iodide, which is yellow, most commonly encountered of the halides is gadolinium chloride. The oxide dissolves in acids to give the salts, such as gadolinium nitrate, Gadolinium, like most lanthanide ions, forms complexes with high coordination numbers. This tendency is illustrated by the use of the chelating agent DOTA, salts of − are useful in magnetic resonance imaging
6.
Silicon
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Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, tin, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, sands, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics. Elemental silicon also has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm. The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
7.
Germanium
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Germanium is a chemical element with symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the group, chemically similar to its group neighbors tin. Pure germanium is a semiconductor with a similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature, unlike silicon, it is too reactive to be found naturally on Earth in the free state. Because it seldom appears in high concentration, germanium was discovered late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earths crust, in 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element along with silver and sulfur, although the new element somewhat resembled arsenic and antimony in appearance, the combining ratios in compounds agreed with Mendeleevs predictions for a relative of silicon. Winkler named the element after his country, Germany, today, germanium is mined primarily from sphalerite, though germanium is also recovered commercially from silver, lead, and copper ores. Germanium metal is used as a semiconductor in transistors and various electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium, today, the amount of germanium produced for semiconductor electronics is one fiftieth the amount of ultra-high purity silicon produced for the same. Presently, the end uses are fibre-optic systems, infrared optics, solar cell applications. Germanium compounds are used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a number of organometallic compounds, such as tetraethylgermane. Germanium is not thought to be an element for any living organism. Some complex organic compounds are being investigated as possible pharmaceuticals. Similar to silicon and aluminum, natural germanium compounds tend to be insoluble in water, however, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins. Because of its position in his Periodic Table, Mendeleev called it ekasilicon, in mid-1885, at a mine near Freiberg, Saxony, a new mineral was discovered and named argyrodite because of the high silver content. The chemist Clemens Winkler analyzed this new mineral, which proved to be a combination of silver, sulfur, Winkler was able to isolate the new element in 1886 and found it similar to antimony
8.
Ancient Greek
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Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Aeolic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are also several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the later Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians, Aeolians, and Ionians, each with their own defining and distinctive dialects. Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
9.
Electrical resistivity and conductivity
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Electrical resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that allows the flow of electric current. Resistivity is commonly represented by the Greek letter ρ, the SI unit of electrical resistivity is the ohm-metre. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity and it is commonly represented by the Greek letter σ, but κ or γ are also occasionally used. Its SI unit is siemens per metre and CGSE unit is reciprocal second, many resistors and conductors have a uniform cross section with a uniform flow of electric current, and are made of one material. All copper wires, irrespective of their shape and size, have approximately the same resistivity, every material has its own characteristic resistivity – for example, resistivity of rubber is far larger than coppers. If the pipes are the size and shape, the pipe full of sand has higher resistance to flow. Resistance, however, is not solely determined by the presence or absence of sand and it also depends on the length and width of the pipe, short or wide pipes have lower resistance than narrow or long pipes. The above equation can be transposed to get Pouillets law, R = ρ ℓ A, the resistance of a given material increases with length, but decreases with increasing cross-sectional area. From the above equations, resistivity has the SI unit ohm metre, the formula R = ρ ℓ / A can be used to intuitively understand the meaning of a resistivity value. For example, if A = 7000100000000000000♠1 m2 ℓ = 7000100000000000000♠1 m, Conductivity, σ, is defined as the inverse of resistivity, σ =1 ρ. Conductivity has SI units of siemens per metre, the above definition was specific to resistors or conductors with a uniform cross-section, where current flows uniformly through them. A more basic and general definition starts from the fact that a field inside a material makes electric current flow. Conductivity is the inverse, σ =1 ρ = J E, for example, rubber is a material with large ρ and small σ—because even a very large electric field in rubber makes almost no current flow through it. On the other hand, copper is a material with small ρ, according to elementary quantum mechanics, electrons in an atom do not take on arbitrary energy values. Rather, electrons only occupy discrete energy levels in an atom or crystal. When a large number of such allowed energy levels are spaced close together —i. e. have similar energies— we can talk about these energy levels together as an energy band. There can be many such bands in a material, depending on the atomic number
10.
Thermal conductivity
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In physics, thermal conductivity is the property of a material to conduct heat. It is evaluated primarily in terms of Fouriers Law for heat conduction, heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are used in heat sink applications. The thermal conductivity of a material may depend on temperature, the reciprocal of thermal conductivity is called thermal resistivity. Thermal conductivity is actually a tensor, which means it is possible to have different values in different directions, in SI units, thermal conductivity is measured in watts per meter-kelvin. The dimension of thermal conductivity is M1L1T−3Θ−1 and these variables are mass, length, time, and temperature. In Imperial units, thermal conductivity is measured in BTU/, other units which are closely related to the thermal conductivity are in common use in the construction and textile industries. The construction industry makes use of such as the R-value. Although related to the conductivity of a material used in an insulation product, R-. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry, there are a number of ways to measure thermal conductivity. Each of these is suitable for a range of materials, depending on the thermal properties. There is a distinction between steady-state and transient techniques, in general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward, the disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar is the most common used for consolidated rock solids. Thermal conductivity is important in science, research, electronics, building insulation and related fields. Several materials are shown in the list of thermal conductivities and these should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper, aluminium, the reciprocal of thermal conductivity is thermal resistivity, usually expressed in kelvin-meters per watt. For a given thickness of a material, that particular constructions thermal resistance, unfortunately, there are differing definitions for these terms
11.
Ductility
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In materials science, ductility is a solid materials ability to deform under tensile stress, this is often characterized by the materials ability to be stretched into a wire. Malleability, a property, is a materials ability to deform under compressive stress. Both of these properties are aspects of plasticity, the extent to which a solid material can be plastically deformed without fracture. Also, these properties are dependent on temperature and pressure. Ductility and malleability are not always coextensive – for instance, while gold has high ductility and malleability, lead has low ductility, the word ductility is sometimes used to encompass both types of plasticity. Ductility is especially important in metalworking, as materials that crack, break or shatter under stress cannot be manipulated using metal-forming processes such as hammering, rolling, malleable materials can be formed cold using stamping or pressing, whereas brittle materials may be cast or thermoformed. High degrees of ductility occur due to bonds, which are found predominantly in metals. In metallic bonds valence shell electrons are delocalized and shared between many atoms, the delocalized electrons allow metal atoms to slide past one another without being subjected to strong repulsive forces that would cause other materials to shatter. Ductility can be quantified by the fracture strain ε f, which is the strain at which a test specimen fractures during a uniaxial tensile test. Another commonly used measure is the reduction of area at fracture q, the ductility of steel varies depending on the alloying constituents. Increasing levels of carbon decrease ductility, many plastics and amorphous solids, such as Play-Doh, are also malleable. The most ductile metal is platinum and the most malleable metal is gold, DBTT is important since, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending or deforming. For example, zamak 3 exhibits good ductility at room temperature, DBTT is a very important consideration in selecting materials that are subjected to mechanical stresses. A similar phenomenon, the transition temperature, occurs with glasses and polymers. In some materials the transition is sharper than others and typically requires a temperature-sensitive deformation mechanism and this can be problematic for steels with a high ferrite content. This famously resulted in serious hull cracking in Liberty ships in colder waters during World War II, DBTT can also be influenced by external factors such as neutron radiation, which leads to an increase in internal lattice defects and a corresponding decrease in ductility and increase in DBTT. The most accurate method of measuring the DBTT of a material is by fracture testing, typically four point bend testing at a range of temperatures is performed on pre-cracked bars of polished material. For experiments conducted at higher temperatures, dislocation activity increases, the temperature at which this occurs is the ductile–brittle transition temperature
12.
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
13.
Gold
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Gold is a chemical element with symbol Au and atomic number 79. In its purest form, it is a bright, slightly yellow, dense, soft, malleable. Chemically, gold is a metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions, Gold often occurs in free elemental form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid solution series with the element silver and also naturally alloyed with copper. Less commonly, it occurs in minerals as gold compounds, often with tellurium, golds atomic number of 79 makes it one of the higher numbered, naturally occurring elements. It is thought to have produced in supernova nucleosynthesis, from the collision of neutron stars. Because the Earth was molten when it was formed, almost all of the present in the early Earth probably sank into the planetary core. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of acid and hydrochloric acid. Gold also dissolves in solutions of cyanide, which are used in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction, as a precious metal, gold has been used for coinage, jewelry, and other arts throughout recorded history. A total of 186,700 tonnes of gold is in existence above ground, the world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry. Gold is also used in infrared shielding, colored-glass production, gold leafing, certain gold salts are still used as anti-inflammatories in medicine. As of 2014, the worlds largest gold producer by far was China with 450 tonnes, Gold is cognate with similar words in many Germanic languages, deriving via Proto-Germanic *gulþą from Proto-Indo-European *ǵʰelh₃-. The symbol Au is from the Latin, aurum, the Latin word for gold, the Proto-Indo-European ancestor of aurum was *h₂é-h₂us-o-, meaning glow. This word is derived from the root as *h₂éu̯sōs, the ancestor of the Latin word Aurora. This etymological relationship is presumably behind the frequent claim in scientific publications that aurum meant shining dawn, Gold is the most malleable of all metals, a single gram can be beaten into a sheet of 1 square meter, and an avoirdupois ounce into 300 square feet. Gold leaf can be thin enough to become semi-transparent
14.
Alloy
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An alloy is a mixture of metals or a mixture of a metal and another element. Alloys are defined by a metallic bonding character, an alloy may be a solid solution of metal elements or a mixture of metallic phases. Intermetallic compounds are alloys with a stoichiometry and crystal structure. Zintl phases are sometimes considered alloys depending on bond types. Alloys are used in a variety of applications. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties, in other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel, solder, brass, pewter, duralumin, bronze, the alloy constituents are usually measured by mass. Alloys are usually classified as substitutional or interstitial alloys, depending on the arrangement that forms the alloy. They can be classified as homogeneous, or heterogeneous or intermetallic. An alloy is a mixture of elements, which forms an impure substance that retains the characteristics of a metal. Alloys are made by mixing two or more elements, at least one of which is a metal and this is usually called the primary metal or the base metal, and the name of this metal may also be the name of the alloy. The other constituents may or may not be metals but, when mixed with the base, they will be soluble. The mechanical properties of alloys will often be different from those of its individual constituents. A metal that is very soft, such as aluminium, can be altered by alloying it with another soft metal. Although both metals are soft and ductile, the resulting aluminium alloy will have much greater strength. Adding a small amount of carbon to iron trades its great ductility for the greater strength of an alloy called steel. Due to its strength, but still substantial toughness, and its ability to be greatly altered by heat treatment, steel is one of the most useful. By adding chromium to steel, its resistance to corrosion can be enhanced, creating stainless steel, while adding silicon will alter its electrical characteristics, producing silicon steel
15.
Stainless steel
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In metallurgy, stainless steel, also known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal. Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This also influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber. When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
16.
Nickel aluminide
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Nickel aluminide is an intermetallic alloy of nickel and aluminum with properties similar to both a ceramic and a metal. Nickel aluminide is unique in that it has high thermal conductivity combined with high strength at high temperature. These properties, combined with its strength and low density, make it ideal for special applications like coating blades in gas turbines. In 2005, the most abrasion-resistant material was created by embedding diamonds in a matrix of nickel aluminide. An alloy of Ni3Al, known as IC-221M, is made up of nickel aluminide combined with other metals including chromium, molybdenum, zirconium. Adding boron increases the ductility of the alloy by positively altering the grain boundary chemistry, the Hall-Petch parameters for this material were σy =163 MPa and ky =8.2 MPaˑcm1/2. Boron increases the hardness of bulk Ni3Al by a similar mechanism and this alloy is extremely strong for its weight, five times stronger than common SAE304 stainless steel. Unlike most alloys, IC-221M increases in strength from room temperature up to 800 °C
17.
Absolute zero
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Absolute zero is the lower limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as 0. The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition, in the quantum-mechanical description, matter at absolute zero is in its ground state, the point of lowest internal energy. And a system at absolute zero still possesses quantum mechanical zero-point energy, the kinetic energy of the ground state cannot be removed. Scientists and technologists routinely achieve temperatures close to zero, where matter exhibits quantum effects such as superconductivity and superfluidity. At temperatures near 0 K, nearly all molecular motion ceases and ΔS =0 for any adiabatic process, in such a circumstance, pure substances can form perfect crystals as T →0. Max Plancks strong form of the law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The Nernst postulate identifies the isotherm T =0 as coincident with the adiabat S =0, although other isotherms, as no two adiabats intersect, no other adiabat can intersect the T =0 isotherm. Consequently no adiabatic process initiated at nonzero temperature can lead to zero temperature, a perfect crystal is one in which the internal lattice structure extends uninterrupted in all directions. The perfect order can be represented by translational symmetry along three axes, every lattice element of the structure is in its proper place, whether it is a single atom or a molecular grouping. For substances that exist in two crystalline forms, such as diamond and graphite for carbon, there is a kind of chemical degeneracy. The question remains whether both can have zero entropy at T =0 even though each is perfectly ordered, using the Debye model, the specific heat and entropy of a pure crystal are proportional to T3, while the enthalpy and chemical potential are proportional to T4. These quantities drop toward their T =0 limiting values and approach with zero slopes, for the specific heats at least, the limiting value itself is definitely zero, as borne out by experiments to below 10 K. Even the less detailed Einstein model shows this curious drop in specific heats, in fact, all specific heats vanish at absolute zero, not just those of crystals. Likewise for the coefficient of thermal expansion, maxwells relations show that various other quantities also vanish. Since the relation between changes in Gibbs free energy, the enthalpy and the entropy is Δ G = Δ H − T Δ S thus, as T decreases, ΔG and ΔH approach each other. Experimentally, it is found that all spontaneous processes result in a decrease in G as they proceed toward equilibrium, if ΔS and/or T are small, the condition ΔG <0 may imply that ΔH <0, which would indicate an exothermic reaction. However, this is not required, endothermic reactions can proceed spontaneously if the TΔS term is large enough, moreover, the slopes of the derivatives of ΔG and ΔH converge and are equal to zero at T =0. e. An actual process is the most exothermic one, one model that estimates the properties of an electron gas at absolute zero in metals is the Fermi gas
18.
Arsenic
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Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in minerals, usually in combination with sulfur and metals. It has various allotropes, but only the form is important to industry. The primary use of arsenic is in alloys of lead. Arsenic is a common dopant in semiconductor electronic devices. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, a few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are a dietary element in rats, hamsters, goats, chickens. However, arsenic poisoning occurs in multicellular life if quantities are larger than needed, Arsenic contamination of groundwater is a problem that affects millions of people across the world. The three most common allotropes are metallic gray, yellow, and black arsenic, with gray being the most common. Gray arsenic adopts a structure consisting of many interlocked, ruffled, six-membered rings. Because of weak bonding between the layers, gray arsenic is brittle and has a relatively low Mohs hardness of 3.5. Nearest and next-nearest neighbors form an octahedral complex, with the three atoms in the same double-layer being slightly closer than the three atoms in the next. This relatively close packing leads to a density of 5.73 g/cm3. Gray arsenic is a semimetal, but becomes a semiconductor with a bandgap of 1. 2–1.4 eV if amorphized, gray arsenic is also the most stable form. Yellow arsenic is soft and waxy, and somewhat similar to tetraphosphorus, both have four atoms arranged in a tetrahedral structure in which each atom is bound to each of the other three atoms by a single bond. This unstable allotrope, being molecular, is the most volatile, least dense, solid yellow arsenic is produced by rapid cooling of arsenic vapor, As 4. It is rapidly transformed into gray arsenic by light, the yellow form has a density of 1.97 g/cm3. Black arsenic is similar in structure to red phosphorus, black arsenic can also be formed by cooling vapor at around 100–220 °C
19.
Antimony
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Antimony is a chemical element with symbol Sb and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite, Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name, kohl. Metallic antimony was known, but it was erroneously identified as lead upon its discovery. In the West, it was first isolated by Vannoccio Biringuccio, for some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods for refining antimony are roasting and reduction with carbon or direct reduction of stibnite with iron, the largest applications for metallic antimony is an alloy with lead and tin and the lead antimony plates in lead–acid batteries. Alloys of lead and tin with antimony have improved properties for solders, bullets, Antimony compounds are prominent additives for chlorine and bromine-containing fire retardants found in many commercial and domestic products. An emerging application is the use of antimony in microelectronics, Antimony is in a pnictogen and has an electronegativity of 2.05. In accordance with periodic trends, it is more electronegative than tin or bismuth, Antimony is stable in air at room temperature, but reacts with oxygen if heated to produce antimony trioxide, Sb2O3. Antimony is resistant to attack by acids, four allotropes of antimony are known, a stable metallic form and three metastable forms. Elemental antimony is a brittle, silver-white shiny metalloid, when slowly cooled, molten antimony crystallizes in a trigonal cell, isomorphic with the gray allotrope of arsenic. A rare explosive form of antimony can be formed from the electrolysis of antimony trichloride, when scratched with a sharp implement, an exothermic reaction occurs and white fumes are given off as metallic antimony forms, when rubbed with a pestle in a mortar, a strong detonation occurs. Black antimony is formed upon cooling of antimony vapor. It has the crystal structure as red phosphorus and black arsenic, it oxidizes in air. At 100 °C, it transforms into the stable form. The yellow allotrope of antimony is the most unstable and it has only been generated by oxidation of stibine at −90 °C. Above this temperature and in ambient light, this metastable allotrope transforms into the more stable black allotrope, elemental antimony adopts a layered structure in which layers consist of fused, ruffled, six-membered rings. The nearest and next-nearest neighbors form an octahedral complex, with the three atoms in each double layer slightly closer than the three atoms in the next. This relatively close packing leads to a density of 6.697 g/cm3
20.
Metalloid
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A metalloid is any chemical element which has properties in between those of metals and nonmetals, or that has a mixture of them. There is neither a standard definition of a metalloid nor complete agreement on the elements appropriately classified as such, despite the lack of specificity, the term remains in use in the literature of chemistry. The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony, five elements are less frequently so classified, carbon, aluminium, selenium, polonium, and astatine. Typical metalloids have an appearance, but they are brittle. Chemically, they behave mostly as nonmetals and they can form alloys with metals. Most of their physical and chemical properties are intermediate in nature. Metalloids are usually too brittle to have any structural uses and they and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics. The electrical properties of silicon and germanium enabled the establishment of the industry in the 1950s. The term metalloid originally referred to nonmetals and its more recent meaning, as a category of elements with intermediate or hybrid properties, became widespread in 1940–1960. Metalloids sometimes are called semimetals, a practice that has been discouraged, in physics it more specifically refers to the electronic band structure of a substance. A metalloid is an element with properties in between, or that are a mixture of, those of metals and nonmetals, and which is hard to classify as either a metal or a nonmetal. This is a definition that draws on metalloid attributes consistently cited in the literature. Difficulty of categorisation is a key attribute, most elements have a mixture of metallic and nonmetallic properties, and can be classified according to which set of properties is more pronounced. Only the elements at or near the margins, lacking a sufficiently clear preponderance of either metallic or nonmetallic properties, are classified as metalloids, boron, silicon, germanium, arsenic, antimony, and tellurium are recognised commonly as metalloids. Depending on the author, one or more from selenium, polonium, boron sometimes is excluded, by itself, or with silicon. Sometimes tellurium is not regarded as a metalloid, the inclusion of antimony, polonium, and astatine as metalloids also has been questioned. Other elements occasionally are classified as metalloids and these elements include hydrogen, beryllium, nitrogen, phosphorus, sulfur, zinc, gallium, tin, iodine, lead, bismuth, and radon. The p-block metals, and nonmetals that can form alloys with metals or modify their properties also have occasionally considered as metalloids
21.
Periodic table
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The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties. This ordering shows periodic trends, such as elements with similar behaviour in the same column and it also shows four rectangular blocks with some approximately similar chemical properties. In general, within one row the elements are metals on the left, the rows of the table are called periods, the columns are called groups. Six groups have names as well as numbers, for example, group 17 elements are the halogens, and group 18, the noble gases. The periodic table can be used to derive relationships between the properties of the elements, and predict the properties of new elements yet to be discovered or synthesized, the periodic table provides a useful framework for analyzing chemical behaviour, and is widely used in chemistry and other sciences. The Russian chemist Dmitri Mendeleev published the first widely recognized periodic table in 1869 and he developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered, Mendeleevs periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. The first 94 elements exist naturally, although some are only in trace amounts and were synthesized in laboratories before being found in nature. Elements with atomic numbers from 95 to 118 have only been synthesized in laboratories or nuclear reactors, synthesis of elements having higher atomic numbers is being pursued. Numerous synthetic radionuclides of naturally occurring elements have also produced in laboratories. Each chemical element has an atomic number representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with variants being referred to as isotopes. Isotopes are never separated in the table, they are always grouped together under a single element. Elements with no stable isotopes have the masses of their most stable isotopes. In the standard periodic table, the elements are listed in order of increasing atomic number, a new row is started when a new electron shell has its first electron. Columns are determined by the configuration of the atom, elements with the same number of electrons in a particular subshell fall into the same columns. Thus, it is easy to predict the chemical properties of an element if one knows the properties of the elements around it
22.
Nonmetal
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In chemistry, a nonmetal is a chemical element that mostly lacks metallic attributes. Seventeen elements are classified as nonmetals, most are gases, one is a liquid. Moving rightward across the standard form of the table, nonmetals adopt structures that have progressively fewer nearest neighbours. Polyatomic nonmetals have structures with either three nearest neighbours, as is the case with carbon, or two nearest neighbours in the case of sulfur, diatomic nonmetals, such as hydrogen, have one nearest neighbour, and the monatomic noble gases, such as helium, have none. This gradual fall in the number of nearest neighbours is associated with a reduction in metallic character, the distinction between the three categories of nonmetals, in terms of receding metallicity is not absolute. Boundary overlaps occur as outlying elements in each category show less-distinct, living organisms are also composed almost entirely of nonmetals, and nonmetals form many more compounds than metals. There is no definition of a nonmetal. They show more variability in their properties than metals do, the following are some of the chief characteristics of nonmetals. The elements generally classified as nonmetals include one element in group 1, one in group 14, the distinction between nonmetals and metals is by no means clear. Nonmetals have structures in each atom usually forms bonds with nearest neighbours. Each atom is able to complete its valence shell and attain a stable noble gas configuration. Exceptions to the rule occur with hydrogen, carbon, nitrogen and oxygen, atoms of the latter three elements are sufficiently small such that they are able to form alternative bonding structures, with fewer nearest neighbours. Thus, carbon is able to form its layered graphite structure, the larger size of the remaining non-noble nonmetals weakens their capacity to form multiple bonds and they instead form two or more single bonds to two or more different atoms. Sulfur, for example, forms an eight-membered molecule in which the atoms are arranged in a ring, a similar pattern occurs more generally, at the level of the entire periodic table, in comparing metals and nonmetals. There is a transition from metallic bonding among the metals on the left of the table through to covalent or Van der Waals bonding among the nonmetals on the right of the table, metallic bonding tends to involve close-packed centrosymmetric structures with a high number of nearest neighbours. Post-transition metals and metalloids, sandwiched between the metals and the nonmetals, tend to have more complex structures with an intermediate number of nearest neighbours. Nonmetallic bonding, towards the right of the table, features open-packed directional structures with fewer or zero nearest neighbours, as is the case with the major categories of metals, metalloids and nonmetals, there is some variation and overlapping of properties within and across each category of nonmetal. Among the polyatomic nonmetals, carbon, phosphorus and selenium—which border the metalloids—begin to show some metallic character, sulfur, is the least metallic of the polyatomic nonmetals but even here shows some discernible metal-like character
23.
Astrophysics
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Astrophysics is the branch of astronomy that employs the principles of physics and chemistry to ascertain the nature of the heavenly bodies, rather than their positions or motions in space. Among the objects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and their emissions are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. In practice, modern astronomical research often involves an amount of work in the realms of theoretical and observational physics. Although astronomy is as ancient as recorded history itself, it was separated from the study of terrestrial physics. Their challenge was that the tools had not yet been invented with which to prove these assertions, for much of the nineteenth century, astronomical research was focused on the routine work of measuring the positions and computing the motions of astronomical objects. Kirchhoff deduced that the lines in the solar spectrum are caused by absorption by chemical elements in the Solar atmosphere. In this way it was proved that the elements found in the Sun. Among those who extended the study of solar and stellar spectra was Norman Lockyer and he thus claimed the line represented a new element, which was called helium, after the Greek Helios, the Sun personified. By 1890, a catalog of over 10,000 stars had been prepared that grouped them into thirteen spectral types, most significantly, she discovered that hydrogen and helium were the principal components of stars. This discovery was so unexpected that her dissertation readers convinced her to modify the conclusion before publication, however, later research confirmed her discovery. By the end of the 20th century, studies of astronomical spectra had expanded to cover wavelengths extending from radio waves through optical, x-ray and it is the practice of observing celestial objects by using telescopes and other astronomical apparatus. The majority of observations are made using the electromagnetic spectrum. Radio astronomy studies radiation with a greater than a few millimeters. The study of these waves requires very large radio telescopes, infrared astronomy studies radiation with a wavelength that is too long to be visible to the naked eye but is shorter than radio waves. Infrared observations are made with telescopes similar to the familiar optical telescopes. Objects colder than stars are studied at infrared frequencies. Optical astronomy is the oldest kind of astronomy, telescopes paired with a charge-coupled device or spectroscopes are the most common instruments used. The Earths atmosphere interferes somewhat with optical observations, so adaptive optics, in this wavelength range, stars are highly visible, and many chemical spectra can be observed to study the chemical composition of stars, galaxies and nebulae
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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
25.
Helium
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Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and its boiling point is the lowest among all the elements. Its abundance is similar to figure in the Sun and in Jupiter. This is due to the high nuclear binding energy of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is believed to have formed during the Big Bang. Large amounts of new helium are being created by fusion of hydrogen in stars. Helium is named for the Greek god of the Sun, Helios and it was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astronomer Jules Janssen. Janssen is jointly credited with detecting the element along with Norman Lockyer, Janssen observed during the solar eclipse of 1868 while Lockyer observed from Britain. Lockyer was the first to propose that the line was due to a new element, the formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in gas fields in parts of the United States. Liquid helium is used in cryogenics, particularly in the cooling of superconducting magnets, a well-known but minor use is as a lifting gas in balloons and airships. As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre, on Earth it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the radioactive decay of heavy radioactive elements. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in short supply. The first evidence of helium was observed on August 18,1868, the line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was assumed to be sodium. He concluded that it was caused by an element in the Sun unknown on Earth, Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος
26.
Nuclear fusion
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In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles. The difference in mass between the products and reactants is manifested as the release of large amounts of energy and this difference in mass arises due to the difference in atomic binding energy between the atomic nuclei before and after the reaction. Fusion is the process that powers active or main sequence stars, the fusion process that produces a nucleus lighter than iron-56 or nickel-62 will generally yield a net energy release. These elements have the smallest mass per nucleon and the largest binding energy per nucleon, the opposite is true for the reverse process, nuclear fission. This means that the elements, such as hydrogen and helium, are in general more fusable, while the heavier elements. The extreme astrophysical event of a supernova can produce energy to fuse nuclei into elements heavier than iron. During the remainder of that decade the steps of the cycle of nuclear fusion in stars were worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, fusion was accomplished in 1951 with the Greenhouse Item nuclear test. Nuclear fusion on a scale in an explosion was first carried out on November 1,1952. Research into developing controlled thermonuclear fusion for civil purposes also began in earnest in the 1950s, the protons are positively charged and repel each other but they nonetheless stick together, demonstrating the existence of another force referred to as nuclear attraction. This force, called the nuclear force, overcomes electric repulsion at very close range. The effect of force is not observed outside the nucleus. The same force also pulls the nucleons together allowing ordinary matter to exist, light nuclei, are sufficiently small and proton-poor allowing the nuclear force to overcome the repulsive Coulomb force. This is because the nucleus is small that all nucleons feel the short-range attractive force at least as strongly as they feel the infinite-range Coulomb repulsion. Building up these nuclei from lighter nuclei by fusion thus releases the energy from the net attraction of these particles. For larger nuclei, however, no energy is released, since the force is short-range. Thus, energy is no longer released when such nuclei are made by fusion, instead, fusion reactions create the light elements that power the stars and produce virtually all elements in a process called nucleosynthesis. The fusion of elements in stars releases energy and the mass that always accompanies it
27.
Metallicity
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In astronomy and physical cosmology, the metallicity or Z is the fraction of mass of a star or other kind of astronomical object that is not in hydrogen or helium. Most of the matter in the universe is in the form of hydrogen and helium, so astronomers use the word metals as a convenient short term for all elements except hydrogen. This usage is distinct from the physical definition of a solid metal. In cosmological terms, the universe is chemically evolving, according to the Big Bang Theory, the early universe first consisted of hydrogen and helium, with trace amounts of lithium and beryllium, but no heavier elements. It is believed that older generations of stars generally have lower metallicities than those of younger generations and these became commonly known as Population I and Population II stars. A third stellar population was introduced in 1978, known as Population III stars and these extremely metal-poor stars were theorised to have been the first-born stars created in the universe. Measurements have demonstrated the connection between a stars metallicity and gas giant planets, like Jupiter and Saturn, the more metals in a star and thus its planetary system and proplyd, the more likely the system may have gas giant planets and rocky planets. Current models show that the metallicity along with the planetary system temperature and distance from the star are key to planet. Metallicity also affects a stars color temperature, metal poor stars are bluer and metal rich stars are redder. The Sun, with 8 planets and 5 planetesimals, is used as the reference, other stars are noted with a positive or negative value. A star with a =0.0 has the iron abundance as the Sun. A star with =−1.0 has one tenth heavy elements of found in the Sun. At =+1, the element abundance is 10 times the Suns value. The survey of population of stars shows that older stars have less metallicity. Stellar composition, as determined by spectroscopy, is simply defined by the parameters X, Y and Z. Here X is the percentage of hydrogen, Y is the fractional percentage of helium. It is simply defined as, X + Y + Z =1.00 In most stars, nebulae and other sources, hydrogen. The hydrogen mass fraction is generally expressed as X ≡ m H M where M is the mass of the system
28.
Construction
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Construction is the process of constructing a building or infrastructure. Construction as an industry comprises six to nine percent of the domestic product of developed countries. Construction starts with planning, design, and financing, and continues until the project is built, large-scale construction requires collaboration across multiple disciplines. An architect normally manages the job, and a manager, design engineer. For the successful execution of a project, effective planning is essential, the largest construction projects are referred to as megaprojects. Construction is a term meaning the art and science to form objects, systems, or organizations. Construction is used as a verb, the act of building, and a noun, how a building was built, in general, there are three sectors of construction, buildings, infrastructure and industrial. Building construction is further divided into residential and non-residential. Infrastructure is often called heavy/highway, heavy civil or heavy engineering and it includes large public works, dams, bridges, highways, water/wastewater and utility distribution. Industrial includes refineries, process chemical, power generation, mills, there are other ways to break the industry into sectors or markets. Engineering News-Record is a magazine for the construction industry. Each year, ENR compiles and reports on data about the size of design and they publish a list of the largest companies in the United States and also a list the largest global firms. In 2014, ENR compiled the data in nine market segments and it was divided as transportation, petroleum, buildings, power, industrial, water, manufacturing, sewer/waste, telecom, hazardous waste plus a tenth category for other projects. In their reporting on the Top 400, they used data on transportation, sewer, hazardous waste, the Standard Industrial Classification and the newer North American Industry Classification System have a classification system for companies that perform or otherwise engage in construction. To recognize the differences of companies in this sector, it is divided into three subsectors, building construction, heavy and civil engineering construction, and specialty trade contractors, there are also categories for construction service firms and construction managers. Building construction is the process of adding structure to real property or construction of buildings, the majority of building construction jobs are small renovations, such as addition of a room, or renovation of a bathroom. Often, the owner of the property acts as laborer, paymaster, for this reason, those with experience in the field make detailed plans and maintain careful oversight during the project to ensure a positive outcome. Residential construction practices, technologies, and resources must conform to local building authority regulations, materials readily available in the area generally dictate the construction materials used
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Home appliance
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Home appliances are electrical/mechanical machines which accomplish some household functions, such as cooling/heating, cooking or cleaning. Brown goods usually require high technical knowledge and skills, while white goods may need more skills and brute force to manipulate the devices. Given a broad usage, the domestic application attached to home appliance is tied to the definition of appliance as an instrument or device designed for a use or function. More specifically, Collins dictionary defines home appliance as, devices or machines, usually electrical, that are in your home, while many appliances have existed for centuries, the self-contained electric or gas powered appliances are a uniquely American innovation that emerged in the twentieth century. The development of these appliances is tied the disappearance of domestic servants. In the early 1900s, electric and gas appliances included washing machines, water heaters, refrigerators, the invention of Earl Richardsons small electric clothes iron in 1903 gave a small initial boost to the home appliance industry. In the Post–World War II economic expansion, the use of dishwashers. Increasing discretionary income was reflected by a rise in home appliances. In America during the 1980s, the industry shipped $1.5 billion worth of each year and employed over 14,000 workers. Throughout this period companies merged and acquired one another to reduce research and production costs and eliminate competitors, in the 1990s, the appliance industry was very consolidated, with over 90% of the products being sold by just five companies. White goods were painted or enameled white, and many of them still are. Small appliances are typically small household electrical machines, easily carried and installed, some such appliances were traditionally finished with genuine or imitation wood. This has become rare but the name has stuck, even for goods that are ever to have had a wooden case. See Life spans of home appliances There is a trend of networking home appliances together, for instance, energy distribution could be managed more evenly so that when a washing machine is on, an oven can go into a delayed start mode, or vice versa. Or, a machine and clothes dryer could share information about load characteristics. Internet-connected home appliances were especially prevalent during recent Consumer Electronic Show events, Appliance recycling consists of dismantling waste home appliances and scrapping their parts for reuse. The main types of appliances that are recycled are T. V. s, refrigerators, air conditioners, washing machines and it involves disassembly, removal of hazardous components and destruction of the equipment to recover materials, generally by shredding, sorting and grading. The Application Research of Small Home Appliance Product Based on Computer Aided Ergonomics, proceedings of the 2012 International Conference of Modern Computer Science and Applications
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Precious metal
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A precious metal is a rare, naturally occurring metallic chemical element of high economic value. Chemically, the precious metals tend to be less reactive than most elements and they are usually ductile and have a high lustre. Historically, precious metals were important as currency but are now regarded mainly as investment, Gold, silver, platinum, and palladium each have an ISO4217 currency code. The best known precious metals are the metals, gold. Although both have industrial uses, they are known for their uses in art, jewelry, fine jewelry. Other precious metals include the platinum metals, ruthenium, rhodium, palladium, osmium, iridium. The demand for metals is driven not only by their practical use but also by their role as investments. Historically, precious metals have commanded much higher prices than common industrial metals, a metal is deemed to be precious if it is rare. The discovery of new sources of ore or improvements in mining or refining processes may cause the value of a metal to diminish. The status of a metal can also be determined by high demand or market value. Precious metals in bulk form are known as bullion and are traded on commodity markets, bullion metals may be cast into ingots or minted into coins. The defining attribute of bullion is that it is valued by its mass, the level of purity varies from issue to issue. The purest mass-produced bullion coins are in the Canadian Gold Maple Leaf series, a 100% pure bullion is nearly impossible, as the percentage of impurities diminishes, it becomes progressively more difficult to purify the metal further. Historically, coins had an amount of weight of alloy. The Krugerrand is the first modern example of measuring in pure gold, other bullion coins show neither the purity nor the fine-gold weight on the coin but are recognized and consistent in their composition. Many coins historically showed a denomination in currency, although nominally issued as legal tender, these coins face value as currency is far below that of their value as bullion. For instance, Canada mints a gold coin at a face value of $50 containing one troy ounce of gold—as of May 2011. Bullion coins minting by national governments gives them some numismatic value in addition to their bullion value, one of the largest bullion coins in the world was the 10, 000-dollar Australian Gold Nugget coin minted in Australia which consists of a full kilogram of 99. 9% pure gold
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Coin
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A coin is a small, flat, round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in quantities at a mint in order to facilitate trade. They are most often issued by a government, Coins are usually metal or alloy, or sometimes made of synthetic materials. Coins made of metal are stored in large quantities as bullion coins. Other coins are used as money in transactions, circulating alongside banknotes. Usually the highest value coin in circulation is less than the lowest-value note. In the last hundred years, the value of circulation coins has occasionally been lower than the value of the metal they contain. Exceptions to the rule of face value being higher than content value also occur for some bullion coins made of copper, silver, or gold, while the Eagle, Maple Leaf, and Sovereign coins have nominal face values, the Krugerrand does not. The first coins were developed independently in Iron Age Anatolia and Archaic Greece, India, Coins spread rapidly in the 6th and 5th centuries BCE, throughout Greece and Persia, and further to the Balkans. Standardized Roman currency was used throughout the Roman Empire, important Roman gold and silver coins were continued into the Middle Ages. Fiat money first arose in medieval China, with the paper money. Early paper money was introduced in Europe in the later Middle Ages, the penny was minted as a silver coin until the 17th century. The first circulating United States coins were cents, produced in 1793, Coins were an evolution of currency systems of the Late Bronze Age, where standard-sized ingots, and tokens such as knife money, were used to store and transfer value. In the late Chinese Bronze Age, standardized cast tokens were made and these were replicas in bronze of earlier Chinese currency, cowrie shells, so they were named Bronze Shell. According to Aristotle and Pollux, the first issuer of coins was Hermodike of Kyme The earliest coins are associated with Iron Age Anatolia. Early electrum coins were not standardized in weight, and in their earliest stage may have been ritual objects, such as badges or medals, issued by priests. The first Lydian coins were made of electrum, a naturally occurring alloy of silver, most of the early Lydian coins include no writing, only an image of a symbolic animal. Anatolian Artemis was the Πὀτνια Θηρῶν, whose symbol was the stag, a small percentage of early Lydian/Greek coins have a legend
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Gallium
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Gallium is a chemical element with symbol Ga and atomic number 31. It is in group 13 of the table, and thus has similarities to the other metals of the group, aluminium, indium. Gallium does not occur as an element in nature, but as gallium compounds in trace amounts in zinc ores. Elemental gallium is a soft, silvery blue metal at standard temperature and pressure, a solid at low temperatures. The melting point of gallium is used as a reference point. The alloy galinstan has a lower melting point of −19 °C. Since its discovery in 1875, gallium has been used to make alloys with low melting points and it is also used in semiconductors as a dopant in semiconductor substrates. Gallium is predominantly used in electronics, gallium arsenide, the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Semiconductive gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes, gallium is also used in the production of artificial gadolinium gallium garnet for jewelry. Gallium has no known role in biology. Gallium behaves in a manner to ferric salts in biological systems. Gallium is used in thermometers as a non-toxic and environmentally friendly alternative to mercury, elemental gallium is not found in nature, but it is easily obtained by smelting. Very pure gallium metal has a color and its solid metal fractures conchoidally like glass. Gallium liquid expands by 3. 1% when it solidifies, therefore, gallium shares the higher-density liquid state with a short list of other materials that includes water, silicon, germanium, antimony, bismuth, and plutonium. Gallium attacks most other metals by diffusing into the metal lattice, for example, it diffuses into the grain boundaries of aluminium-zinc alloys and steel, making them very brittle. Gallium easily alloys with metals, and is used in small quantities in the plutonium-gallium alloy in the plutonium cores of nuclear bombs to stabilize the plutonium crystal structure. The melting point of gallium, at 302.9146 K, is just above room temperature and this melting point is one of the formal temperature reference points in the International Temperature Scale of 1990 established by the International Bureau of Weights and Measures. The triple point of gallium,302.9166 K, is used by the US National Institute of Standards, the unique melting point of gallium allows it to melt in the human hand, and then refreeze if removed
33.
Lustre (mineralogy)
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Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning light, a range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky. Similarly, the term refers to a glassy lustre. A list of terms is given below. Lustre varies over a continuum, and so there are no rigid boundaries between the different types of lustre. The terms are frequently combined to describe types of lustre. Some minerals exhibit unusual optical phenomena, such as asterism or chatoyancy, a list of such phenomena is given below. Adamantine minerals possess a superlative lustre, which is most notably seen in diamond, such minerals are transparent or translucent, and have a high refractive index. Minerals with an adamantine lustre are uncommon, with examples being cerussite. Minerals with a degree of lustre are referred to as subadamantine, with some examples being garnet. Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, a distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, and having even less lustre. Greasy minerals resemble fat or grease, a greasy lustre often occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite. Many minerals with a greasy lustre also feel greasy to the touch, metallic minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite, pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls, such minerals possess perfect cleavage, with examples including muscovite and stilbite. Resinous minerals have the appearance of resin, chewing gum or plastic, a principal example is amber, which is a form of fossilized resin. Silky minerals have an arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos, ulexite and the satin spar variety of gypsum, a fibrous lustre is similar, but has a coarser texture
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Gold leaf
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Gold leaf is gold that has been hammered into thin sheets by goldbeating and is often used for gilding. Gold leaf is available in a variety of karats and shades. The most commonly used gold is 22-karat yellow gold, Gold leaf is a type of metal leaf, but the term is rarely used when referring to gold leaf. The term metal leaf is used for thin sheets of metal of any color that do not contain any real gold. Real yellow gold leaf is about 91. 7% pure gold, silver colored white gold is approximately 50% pure gold. Layering gold leaf over a surface is called gold leafing or gilding, traditional water gilding is the most difficult and highly regarded form of gold leafing. It has remained unchanged for hundreds of years and is still done by hand. Gold leaf is used in art in a raw state. It has been used in jewellery in various periods, often as small pieces hanging freely. Gold glass is gold leaf held between two pieces of glass, and was used for decorated Ancient Roman vessels, where some of the gold was scraped off to form an image, Gold leaf is also used in Buddhist art to decorate statues and symbols. Gold leafing can also be seen on domes in religious and public architecture, from the ancient temples to modern day buildings, gold leaf has been an integral component of architecture to designate important structures since the dawn of humankind. Due to gold’s resilience, golden-domed buildings can stand up to weather, deterioration and even modern pollution, Gold in architecture became an integral component of Byzantine and Roman churches and basilicas in 400 AD, most notably Basilica di Santa Maria Maggiore in Rome. The church was built by Pope Sixtus III and is one of the earliest examples of gold mosaics, the mosaics were made of stone, tile or glass backed on gold leaf walls, giving the church a beautifully intricate backdrop. The 14th century campanile, or bell tower, is the highest in Rome, the apse mosaic, the Coronation of the Virgin, is from 1295, signed by the Franciscan friar, Jacopo Torriti. It is also the location of ceremonial spaces, such as the Hall of Honour, the Memorial Chamber. Capping the room is a ceiling with deep octagonal coffers, each filled with heraldic symbols, including maple leaves, fleur-de-lis, lions rampant, clàrsach, Welsh Dragons. This plane rests on six pairs and four pilasters, each of which is capped by a caryatid. Below the windows is an architrave, broken only by baldachins at the base of each of the above pilasters
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Cleavage (crystal)
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Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. Cleavage forms parallel to planes, Basal or pinacoidal cleavage occurs when there is only one cleavage plane. Mica also has basal cleavage, this is why mica can be peeled into thin sheets, cubic cleavage occurs on when there are three cleavage planes intersecting at 90 degrees. Halite has cubic cleavage, and therefore, when halite crystals are broken, octahedral cleavage occurs when there are four cleavage planes in a crystal. Octahedral cleavage is common for semiconductors, rhombohedral cleavage occurs when there are three cleavage planes intersecting at angles that are not 90 degrees. Prismatic cleavage occurs when there are two planes in a crystal. Dodecahedral cleavage occurs when there are six cleavage planes in a crystal, crystal parting occurs when minerals break along planes of structural weakness due to external stress or along twin composition planes. Parting breaks are very similar in appearance to cleavage, but only due to stress. Examples include magnetite which shows octahedral parting, the parting of corundum. Cleavage is a property traditionally used in mineral identification, both in hand specimen and microscopic examination of rock and mineral studies. As an example, the angles between the cleavage planes for the pyroxenes and the amphiboles are diagnostic. Crystal cleavage is of importance in the electronics industry and in the cutting of gemstones. Precious stones are generally cleaved by impact, as in diamond cutting, synthetic single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Elemental semiconductors are diamond cubic, a group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved, most other commercial semiconductors can be made in the related zinc blende structure, with similar cleavage planes. Cleavage Mineral galleries, Mineral properties – Cleavage
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Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
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Lithium
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Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the metal group of chemical elements. Under standard conditions, it is the lightest metal and the least dense solid element, like all alkali metals, lithium is highly reactive and flammable. For this reason, it is stored in mineral oil. When cut open, it exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a silvery gray. Because of its reactivity, lithium never occurs freely in nature, and instead, appears only in compounds. Lithium occurs in a number of minerals, but due to its solubility as an ion, is present in ocean water and is commonly obtained from brines. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride, the nucleus of the lithium atom verges on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight. For related reasons, lithium has important links to nuclear physics, the transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium-6 deuteride serves as a fusion fuel in staged thermonuclear weapons. These uses consume more than three quarters of lithium production, Lithium is found in variable amounts in foods, primary food sources are grains and vegetables, in some areas, the drinking water also provides significant amounts of the element. Human dietary lithium intakes depend on location and the type of foods consumed, traces of lithium were detected in human organs and fetal tissues already in the late 19th century, leading to early suggestions as to possible specific functions in the organism. However, it took another century until evidence for the essentiality of lithium became available, in studies conducted from the 1970s to the 1990s, rats and goats maintained on low-lithium rations were shown to exhibit higher mortalities as well as reproductive and behavioral abnormalities. Lithium appears to play an important role during the early fetal development as evidenced by the high lithium contents of the embryo during the early gestational period. The available experimental evidence now appears to be sufficient to accept lithium as essential, the lithium ion Li+ administered as any of several lithium salts has proven to be useful as a mood-stabilizing drug in the treatment of bipolar disorder in humans. Like the other metals, lithium has a single valence electron that is easily given up to form a cation. Because of this, lithium is a conductor of heat and electricity as well as a highly reactive element. Lithiums low reactivity is due to the proximity of its electron to its nucleus
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Osmium
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Osmium is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the group that is found as a trace element in alloys. Osmium is the densest naturally occurring element, with a density of 22.59 g/cm3, Osmium has a blue-gray tint and is the densest stable element, approximately twice the density of lead and slightly denser than iridium. Calculations of density from the X-ray diffraction data may produce the most reliable data for these elements, Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility, correspondingly, its bulk modulus is extremely high, reported between 395 and 462 GPa, which rivals that of diamond. The hardness of osmium is moderately high at 4 GPa, because of its hardness, brittleness, low vapor pressure, and very high melting point, solid osmium is difficult to machine, form, or work. Osmium forms compounds with oxidation states ranging from −2 to +8, the most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element aside from iridiums +9 and is encountered only in xenon, ruthenium, hassium, and iridium. The oxidation states −1 and −2 represented by the two reactive compounds Na 2 and Na 2 are used in the synthesis of osmium cluster compounds, the most common compound exhibiting the +8 oxidation state is osmium tetroxide. This toxic compound is formed when powdered osmium is exposed to air and it is a very volatile, water-soluble, pale yellow, crystalline solid with a strong smell. Osmium powder has the smell of osmium tetroxide. Osmium tetroxide forms red osmates OsO 42−2 upon reaction with a base, with ammonia, it forms the nitrido-osmates OsO 3N−. Osmium tetroxide boils at 130 °C and is an oxidizing agent. By contrast, osmium dioxide is black, non-volatile, and much less reactive, Osmium pentafluoride is known, but osmium trifluoride has not yet been synthesized. The lower oxidation states are stabilized by the halogens, so that the trichloride, tribromide, triiodide. The oxidation state +1 is known only for osmium iodide, whereas several carbonyl complexes of osmium, such as triosmium dodecacarbonyl, in general, the lower oxidation states of osmium are stabilized by ligands that are good σ-donors and π-acceptors. The higher oxidation states are stabilized by strong σ- and π-donors, such as O2−, despite its broad range of compounds in numerous oxidation states, osmium in bulk form at ordinary temperatures and pressures resists attack by all acids and alkalis, including aqua regia. Osmium has seven naturally occurring isotopes, six of which are stable, 184Os, 187Os, 188Os, 189Os, 190Os, and 192Os
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Crystal structure
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In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the pattern is the unit cell of the structure. The unit cell completely defines the symmetry and structure of the crystal lattice. The repeating patterns are said to be located at the points of the Bravais lattice, the lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters. The symmetry properties of the crystal are described by the concept of space groups, all possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups. The crystal structure and symmetry play a role in determining many physical properties, such as cleavage, electronic band structure. The crystal structure of a material can be described in terms of its unit cell, the unit cell is a box containing one or more atoms arranged in three dimensions. The unit cells stacked in three-dimensional space describe the arrangement of atoms of the crystal. Commonly, atomic positions are represented in terms of fractional coordinates, the atom positions within the unit cell can be calculated through application of symmetry operations to the asymmetric unit. The asymmetric unit refers to the smallest possible occupation of space within the unit cell and this does not, however imply that the entirety of the asymmetric unit must lie within the boundaries of the unit cell. Symmetric transformations of atom positions are calculated from the group of the crystal structure. Vectors and planes in a lattice are described by the three-value Miller index notation. It uses the indices ℓ, m, and n as directional parameters, which are separated by 90°, by definition, the syntax denotes a plane that intercepts the three points a1/ℓ, a2/m, and a3/n, or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell, if one or more of the indices is zero, it means that the planes do not intersect that axis. A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined, the Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in, in an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of a vector normal to the plane. Likewise, the planes are geometric planes linking nodes
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Body-centered cubic
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In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals, there are three main varieties of these crystals, Primitive cubic Body-centered cubic, Face-centered cubic Each is subdivided into other variants listed below. Note that although the cell in these crystals is conventionally taken to be a cube. This is related to the fact that in most cubic crystal systems, a classic isometric crystal has square or pentagonal faces. The three Bravais lattices in the crystal system are, The primitive cubic system consists of one lattice point on each corner of the cube. Each atom at a point is then shared equally between eight adjacent cubes, and the unit cell therefore contains in total one atom. The body-centered cubic system has one point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell, Each sphere in a cF lattice has coordination number 12. The face-centered cubic system is related to the hexagonal close packed system. The plane of a cubic system is a hexagonal grid. Attempting to create a C-centered cubic crystal system would result in a simple tetragonal Bravais lattice, there are a total 36 cubic space groups. Other terms for hexoctahedral are, normal class, holohedral, ditesseral central class, a simple cubic unit cell has a single cubic void in the center. Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void and these tetrahedral voids are not local maxima and are not technically voids, but they do occasionally appear in multi-atom unit cells. A face-centered cubic unit cell has eight tetrahedral voids located midway between each corner and the center of the cell, for a total of eight net tetrahedral voids. One important characteristic of a structure is its atomic packing factor. This is calculated by assuming all the atoms are identical spheres. The atomic packing factor is the proportion of space filled by these spheres, assuming one atom per lattice point, in a primitive cubic lattice with cube side length a, the sphere radius would be a⁄2 and the atomic packing factor turns out to be about 0.524. Similarly, in a bcc lattice, the atomic packing factor is 0.680, as a rule, since atoms in a solid attract each other, the more tightly packed arrangements of atoms tend to be more common
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Cubic crystal system
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In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals, there are three main varieties of these crystals, Primitive cubic Body-centered cubic, Face-centered cubic Each is subdivided into other variants listed below. Note that although the cell in these crystals is conventionally taken to be a cube. This is related to the fact that in most cubic crystal systems, a classic isometric crystal has square or pentagonal faces. The three Bravais lattices in the crystal system are, The primitive cubic system consists of one lattice point on each corner of the cube. Each atom at a point is then shared equally between eight adjacent cubes, and the unit cell therefore contains in total one atom. The body-centered cubic system has one point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell, Each sphere in a cF lattice has coordination number 12. The face-centered cubic system is related to the hexagonal close packed system. The plane of a cubic system is a hexagonal grid. Attempting to create a C-centered cubic crystal system would result in a simple tetragonal Bravais lattice, there are a total 36 cubic space groups. Other terms for hexoctahedral are, normal class, holohedral, ditesseral central class, a simple cubic unit cell has a single cubic void in the center. Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void and these tetrahedral voids are not local maxima and are not technically voids, but they do occasionally appear in multi-atom unit cells. A face-centered cubic unit cell has eight tetrahedral voids located midway between each corner and the center of the cell, for a total of eight net tetrahedral voids. One important characteristic of a structure is its atomic packing factor. This is calculated by assuming all the atoms are identical spheres. The atomic packing factor is the proportion of space filled by these spheres, assuming one atom per lattice point, in a primitive cubic lattice with cube side length a, the sphere radius would be a⁄2 and the atomic packing factor turns out to be about 0.524. Similarly, in a bcc lattice, the atomic packing factor is 0.680, as a rule, since atoms in a solid attract each other, the more tightly packed arrangements of atoms tend to be more common
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Close-packing of equal spheres
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In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement. Carl Friedrich Gauss proved that the highest average density – that is, the same packing density can also be achieved by alternate stackings of the same close-packed planes of spheres, including structures that are aperiodic in the stacking direction. The Kepler conjecture states that this is the highest density that can be achieved by any arrangement of spheres and this conjecture was proven by T. C. Highest density is only in case of 1,2,3,8 and 24 dimensions. Many crystal structures are based on a close-packing of a kind of atom. The cubic and hexagonal arrangements are very close to one another in energy, there are two simple regular lattices that achieve this highest average density. They are called face-centered cubic and hexagonal close-packed, based on their symmetry, both are based upon sheets of spheres arranged at the vertices of a triangular tiling, they differ in how the sheets are stacked upon one another. The fcc lattice is known to mathematicians as that generated by the A3 root system. Cannonballs were usually piled in a rectangular or triangular wooden frame, both arrangements produce a face-centered cubic lattice – with different orientation to the ground. Hexagonal close-packing would result in a pyramid with a hexagonal base. In both the fcc and hcp arrangements each sphere has twelve neighbors, for every sphere there is one gap surrounded by six spheres and two smaller gaps surrounded by four spheres. The distances to the centers of these gaps from the centers of the spheres is √ 3⁄2 for the tetrahedral, and √2 for the octahedral. Relative to a layer with positioning A, two more positionings B and C are possible. Every sequence of A, B, and C without immediate repetition of the one is possible. The most regular ones are fcc = ABCABCA hcp = ABABABA, in close-packing, the center-to-center spacing of spheres in the xy plane is a simple honeycomb-like tessellation with a pitch of one sphere diameter. The coordination number of hcp and fcc is 12 and their atomic packing factors are equal to the mentioned above,0.74. The distance between the centers along the shortest path namely that straight line will therefore be r1 + r2 where r1 is the radius of the first sphere, in close packing all of the spheres share a common radius, r. Therefore two centers would simply have a distance 2r, hexagonal close packing of spheres, the coordinate points of the lattice will be the spheres centers
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Transition metal
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Many scientists describe a transition metal as any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table. In actual practice, the lanthanide and actinide series are also considered transition metals and are called inner transition metals. Cotton and Wilkinson expand the brief IUPAC definition by specifying which elements are included, as well as the elements of groups 4 to 11, they add scandium and yttrium in group 3 which have a partially filled d subshell in the metallic state. These last two elements are included even though they do not seem to possess the properties which are so characteristic of the transition metals in general. Lanthanum and actinium in Group 3 are however classified as lanthanides and actinides respectively and these elements are now known as the d-block. In the d-block the atoms of the elements have between 1 and 10 d electrons, Sc and Y in Group 3 are also generally recognized as transition metals. However the elements La–Lu and Ac–Lr and Group 12 attract different definitions from different authors, many chemistry textbooks and printed periodic tables classify La and Ac as Group 3 elements and transition metals, since their atomic ground-state configurations are s2d1 like Sc and Y. The elements Ce-Lu are considered as the series and Th-Lr as the actinide series. The two series together are classified as elements, or as inner transition elements. Some inorganic chemistry textbooks include La with the lanthanides and Ac with the actinides, a third classification defines the f-block elements as La-Yb and Ac-No, while placing Lu and Lr in Group 3. This is based on the Aufbau principle for filling electron subshells, in which 4f is filled before 5d, zinc, cadmium, and mercury are generally excluded from the transition metals as they have the electronic configuration d10s2, with no incomplete d shell. In the oxidation state +2 the ions have the electronic configuration d10, however, these elements can exist in other oxidation states, including the +1 oxidation state, as in the diatomic ion Hg2+2. The group 12 elements Zn, Cd and Hg may therefore, under certain rules, however, it is often convenient to include these elements in a discussion of the transition elements. Another example occurs in the Irving-Williams series of stability constants of complexes, although meitnerium, darmstadtium, and roentgenium are within the d-block and are expected to behave as transition metals, this has not yet been experimentally confirmed. The general electronic configuration of the elements is d1, 10n s1,2. The period 6 and 7 transition metals also add f1,14 electrons and this rule is however only approximate – it only holds for some of the transition elements, and only then in their neutral ground state. The d-sub-shell is the next-to-last sub-shell and is denoted as d -sub-shell, the number of s electrons in the outermost s sub-shell is generally one or two except palladium, with no electron in that s-sub shell in its ground state. The s-sub-shell in the shell is represented as the ns sub-shell
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Body-centered cubic unit cell as found in e.g. chromium, iron, and tungsten
Face-centered cubic unit cell, as found in e.g. aluminium, copper, and gold
Hexagonal close-packed unit cell, as found in e.g. titanium, cobalt, and zinc
Niobium crystals, and a 1 cm3 anodized niobium cube for comparison
Molybdenum crystals, and a 1 cm3 niobium cube for comparison
Tantalum single crystal, some crystalline fragments, and a 1 cm3 tantalum cube for comparison
Tungsten rods with evaporated crystals, partially oxidized with colorful tarnish, and a 1 cm3 tungsten cube for comparison
Rhenium single crystal, a remelted bar, and a 1 cm3 rhenium cube for comparison
Gold crystals
Crystalline silver
A slice of meteoric iron
A droplet of solidified molten tin
Arsenic, sealed in a container to prevent tarnishing
Zinc fragments and a 1 cm3 cube
Antimony, showing its brilliant lustre
Bismuth in crystalline form, with a very thin oxidation layer, and a 1 cm3 bismuth cube
Sodium
Potassium pearls under paraffin oil. Size of the largest pearl is 0.5 cm.
Strontium crystals
Aluminium chunk,
A bar of titanium crystals
Scandium, including a 1 cm3 cube.jpg)
Lutetium, including a 1 cm3 cube
Hafnium, in the form of a 1.7 kg bar
