Water is a transparent, tasteless and nearly colorless chemical substance, the main constituent of Earth's streams and oceans, the fluids of most living organisms. It is vital for all known forms of life though it provides no calories or organic nutrients, its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient pressure, it forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of its solid state; when finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is water vapor. Water moves continually through the water cycle of evaporation, condensation and runoff reaching the sea. Water covers 71% of the Earth's surface in seas and oceans. Small portions of water occur as groundwater, in the glaciers and the ice caps of Antarctica and Greenland, in the air as vapor and precipitation.
Water plays an important role in the world economy. 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers and canals. Large quantities of water and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances. Water is central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, sport fishing, diving; the word water comes from Old English wæter, from Proto-Germanic *watar, from Proto-Indo-European *wod-or, suffixed form of root *wed-. Cognate, through the Indo-European root, with Greek ύδωρ, Russian вода́, Irish uisce, Albanian ujë; the identification of water as a substance Water is a polar inorganic compound, at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue.
This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the "universal solvent" for its ability to dissolve many substances. This allows it to be the "solvent of life", it is the only common substance to exist as a solid and gas in normal terrestrial conditions. Water is a liquid at the pressures that are most adequate for life. At a standard pressure of 1 atm, water is a liquid between 0 and 100 °C. Increasing the pressure lowers the melting point, about −5 °C at 600 atm and −22 °C at 2100 atm; this effect is relevant, for example, to ice skating, to the buried lakes of Antarctica, to the movement of glaciers. Increasing the pressure has a more dramatic effect on the boiling point, about 374 °C at 220 atm; this effect is important in, among other things, deep-sea hydrothermal vents and geysers, pressure cooking, steam engine design. At the top of Mount Everest, where the atmospheric pressure is about 0.34 atm, water boils at 68 °C. At low pressures, water cannot exist in the liquid state and passes directly from solid to gas by sublimation—a phenomenon exploited in the freeze drying of food.
At high pressures, the liquid and gas states are no longer distinguishable, a state called supercritical steam. Water differs from most liquids in that it becomes less dense as it freezes; the maximum density of water in its liquid form is 1,000 kg/m3. The density of ice is 917 kg/m3. Thus, water expands 9% in volume as it freezes, which accounts for the fact that ice floats on liquid water; the details of the exact chemical nature of liquid water are not well understood. Pure water is described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths, frogs are known to be able to smell it. However, water from ordinary sources has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water by avoiding water, too salty or putrid; the apparent color of natural bodies of water is determined more by dissolved and suspended solids, or by reflection of the sky, than by water itself.
Light in the visible electromagnetic spectrum can traverse a couple meters of pure water without significant absorption, so that it looks transparent and colorless. Thus aquatic plants and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. Water vapour is invisible as a gas. Through a thickness of 10 meters or more, the intrinsic color of water is visibly turquoise, as its absorption spectrum has
Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. The prefix di- is of Greek origin, meaning "two". If a diatomic molecule consists of two atoms of the same element, such as hydrogen or oxygen it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide or nitric oxide, the molecule is said to be heteronuclear; the only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure are the gases hydrogen, oxygen and chlorine. The noble gases are gases at STP, but they are monatomic; the homonuclear diatomic gases and noble gases together are called "elemental gases" or "molecular gases", to distinguish them from other gases that are chemical compounds. At elevated temperatures, the halogens bromine and iodine form diatomic gases. All halogens have been observed as diatomic molecules, except for astatine, uncertain; the mnemonics BrINClHOF, pronounced "Brinklehof", HONClBrIF, pronounced "Honkelbrif", HOFBrINCl have been coined to aid recall of the list of diatomic elements.
Other elements form diatomic molecules when evaporated, but these diatomic species repolymerize when cooled. Heating elemental phosphorus gives diphosphorus, P2. Sulfur vapor is disulfur. Dilithium is known in the gas phase. Ditungsten and dimolybdenum form with sextuple bonds in the gas phase; the bond in a homonuclear diatomic molecule is non-polar. Dirubidium is diatomic. All other diatomic molecules are chemical compounds of two different elements. Many elements can combine to form heteronuclear diatomic molecules, depending on temperature and pressure; some examples include, gases carbon monoxide, nitric oxide, hydrogen chloride. Many 1:1 binary compounds are not considered diatomic because they are polymeric at room temperature, but they form diatomic molecules when evaporated, for example gaseous MgO, SiO, many others. Hundreds of diatomic molecules have been identified in the environment of the Earth, in the laboratory, in interstellar space. About 99% of the Earth's atmosphere is composed of two species of diatomic molecules: nitrogen and oxygen.
The natural abundance of hydrogen in the Earth's atmosphere is only of the order of parts per million, but H2 is the most abundant diatomic molecule in the universe. The interstellar medium is, dominated by hydrogen atoms. Diatomic elements played an important role in the elucidation of the concepts of element and molecule in the 19th century, because some of the most common elements, such as hydrogen and nitrogen, occur as diatomic molecules. John Dalton's original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would have the simplest atomic ratios with respect to one another. For example, Dalton assumed water's formula to be HO, giving the atomic weight of oxygen as eight times that of hydrogen, instead of the modern value of about 16; as a consequence, confusion existed regarding atomic weights and molecular formulas for about half a century. As early as 1805, Gay-Lussac and von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen, by 1811 Amedeo Avogadro had arrived at the correct interpretation of water's composition, based on what is now called Avogadro's law and the assumption of diatomic elemental molecules.
However, these results were ignored until 1860 due to the belief that atoms of one element would have no chemical affinity toward atoms of the same element, partly due to apparent exceptions to Avogadro's law that were not explained until in terms of dissociating molecules. At the 1860 Karlsruhe Congress on atomic weights, Cannizzaro resurrected Avogadro's ideas and used them to produce a consistent table of atomic weights, which agree with modern values; these weights were an important prerequisite for the discovery of the periodic law by Dmitri Mendeleev and Lothar Meyer. Diatomic molecules are in their lowest or ground state, which conventionally is known as the X state; when a gas of diatomic molecules is bombarded by energetic electrons, some of the molecules may be excited to higher electronic states, as occurs, for example, in the natural aurora. Such excitation can occur when the gas absorbs light or other electromagnetic radiation; the excited states are unstable and relax back to the ground state.
Over various short time scales after the excitation, transitions occur from higher to lower electronic states and to the ground state, in each transition results a photon is emitted. This emission is known as fluorescence. Successively higher electronic states are conventionally named A, B, C, etc.. The excitation energy must be greater than or equal to the energy of the electronic state in order for the excitation to occur. In quantum theory, an electronic state of a diatomic molecule is represented by 2 S + 1 Λ ( v
Argonium, an ion combining a proton and an argon atom, can be made in an electric discharge, was the first noble gas molecular ion to be found in interstellar space. Argonium is isoelectronic with hydrogen chloride, its dipole moment is 2.18 D for the ground state. The binding energy is 369 kJ mol−1; this is smaller than that of H+3 and many other protonated species, but more than that of H+2. Lifetimes of different vibrational states vary with isotope and become shorter for the more rapid high-energy vibrations. For ArH+ v=1 2.28, v=2 1.2, v=3 0.85, v=4 0.64, v=5 0.46 ms For ArD+ 9.09, 4.71, 3.27, 2.55, 2.11 msThe force constant in the bond is calculated at 3.88 mdyne/Å2. ArH+ + H2 → Ar + H+3 ArH+ + C → Ar + CH+ ArH+ + N → Ar + NH+ ArH+ + O → Ar + OH+ ArH+ + CO → Ar + COH+But the reverse reaction happens: Ar + H+2 → ArH+ + H. Ar + H+3 → *ArH+ + H2Ar+ + H2 has a cross section of 10−18 m2 for low energy, it drops off for energies over 100 eV Ar + H+2 has a cross sectional area of 6×10−19 m2 for low energy H+2, but when the energy exceeds 10 eV yield reduces, more Ar+ and H2 is produced instead.
Ar + H+3 has a maximum yield of ArH+ for energies between 0.75 and 1 eV with a cross section of 5×10−20 m2. 0.6 eV is needed to make the reaction proceed forward. Over 4eV more Ar+ and H starts to appear. Argonium is produced from Ar+ ions produced by cosmic rays and X-rays from neutral argon. Ar+ + H2 → *ArH+ + H 1.49 eVWhen ArH+ encounters an electron, dissociative recombination can occur, but it is slow for lower energy electrons, allowing ArH+ to survive for a much longer time than many other similar protonated cations. ArH+ + e− → Ar + HBecause ionisation potential of argon atoms is lower than that of the hydrogen molecule, the argon ion reacts with molecular hydrogen, but for helium and neon ions, they will strip an electron from a hydrogen molecule. Ar+ + H2 → ArH+ + H Ne+ + H2 → Ne + H+ + H He+ + H2 → He + H+ + H Artificial ArH+ made from earthly argon contains the isotope 40Ar rather than the cosmically abundant 36Ar. Artificially it is made by an electric discharge through an argon-hydrogen mixture.
Brault and Davis were the first to detect the molecule using infrared spectroscopy to observe vibration-rotation bands. The UV spectrum has two absorption points resulting in the ion breaking up; the 11.2 eV conversion to the B1Π state has a low dipole and so does not absorb much. A 15.8 eV to a repulsive A1Σ+ state is at a shorter wavelength than the Lymann limit, so there are few photons around to do this in space. ArH+ occurs in interstellar diffuse atomic hydrogen gas. For argonium to form, the fraction of molecular hydrogen H2 must be in the range 0.0001 to 0.001. Different molecular ions form in correlation with different concentrations of H2. Argonium is detected by its absorption lines at 617.525 GHz, 1234.602 GHz. These lines are due to the isotopolog 36Ar1H+ undergoing rotational transitions; the lines have been detected in the direction of the galactic centre SgrB2 and SgrB2, G34.26+0.15, W31C, W49, W51e, however where absorption lines are observed, argonium is not to be in the microwave source, but instead in the gas in front of it.
Emission lines are found in the Crab Nebula. In the Crab Nebula ArH+ occurs in several spots revealed by emission lines; the strongest place is in the Southern Filament. This is the place with the strongest concentration of Ar+ and Ar2+ ions; the column density of ArH + in the Crab Nebula is between 1013 atoms per square centimeter. Possible the energy required to excite the ions so that can emit comes from collisions with electrons or hydrogen molecules. Towards the Milky Way centre the column density of ArH+ is around 2×1013 cm−2. Two isotopologs of argonium 36ArH+ and 38ArH+ are known to be in a distant unnamed galaxy with z=0.88582, on the line of sight to the blazar PKS 1830−211. Electron neutralization and destruction of argonium outcompletes the formation rate in space if the H2 concentration is below 1 in 10−4. Using the McMath solar Fourier transform spectrometer at Kitt Peak National Observatory, James W. Brault and Sumner P. Davis observed ArH+ vibration-rotation infrared lines for the first time.
J. W. C. Johns observed the infrared spectrum. Argon facilitates the reaction of tritium with double bonds in fatty acids by forming an ArT+ intermediate; when gold is sputtered with an argon-hydrogen plasma, the actual displacement of gold is done by ArH+. Argonium is the name of a major tectonic scarp on the edge of the Rheasilvia impact basin in the Quadrangle Av-12 on 4 Vesta. Argonium is an erroneous name for Argon
Potassium chloride is a metal halide salt composed of potassium and chlorine. It has a white or colorless vitreous crystal appearance; the solid dissolves in water and its solutions have a salt-like taste. KCl is used as a fertilizer, in medicine, in scientific applications, in food processing, where it may be known as E number additive E508. In a few states of the United States it is used to cause cardiac arrest as the third drug in the "three drug cocktail" for executions by lethal injection, it occurs as the mineral sylvite, in combination with sodium chloride as sylvinite. The majority of the potassium chloride produced is used for making fertilizer, called potash, since the growth of many plants is limited by potassium availability; the two main types of potash are: Muriate of Sulphate of Potash. While SOP sells at a premium to MOP, the vast majority of potash fertilizer worldwide is sold as MOP. Potassium is vital in the human body, potassium chloride by mouth is the common means to treat low blood potassium, although it can be given intravenously.
The intravenous form is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. It can be used as a salt substitute for food, but due to its weak, unsalty flavor, it is mixed with ordinary table salt improve the taste to form low sodium salt; the addition of 1 ppm of thaumatin reduces this bitterness. Complaints of bitterness or a chemical or metallic taste are reported with potassium chloride used in food; as a chemical feedstock, it is used for the manufacture of potassium potassium metal. It is used in medicine, lethal injections, scientific applications, food processing, as a sodium-free substitute for table salt for people concerned about the health effects of sodium, it is used as a supplement in animal feed to boost the amount of nutrients in the feed, which in turn promotes healthy growth in animals. As an added benefit, it is known to increase milk production, it is sometimes used in water as a completion fluid in petroleum and natural gas operations, as well as being an alternative to sodium chloride in household water softener units.
Glass manufacturers use granular potash as a flux, lowering the temperature at which a mixture melts. Because potash confers excellent clarity to glass, it is used in eyeglasses, glassware and computer monitors. KCl is useful as a beta radiation source for calibration of radiation monitoring equipment, because natural potassium contains 0.0118% of the isotope 40K. One kilogram of KCl yields 16350 becquerels of radiation consisting of 89.28% beta and 10.72% gamma with 1.46083 MeV. Potassium chloride is used in some de-icing products that are designed to be safer for pets and plants, though these are inferior in melting quality to calcium chloride, it is used in various brands of bottled water, as well as in bulk quantities for fossil fuel drilling purposes. Potassium chloride was once used as a fire extinguishing agent, used in portable and wheeled fire extinguishers. Known as Super-K dry chemical, it was more effective than sodium bicarbonate-based dry chemicals and was compatible with protein foam.
This agent fell out of favor with the introduction of potassium bicarbonate dry chemical in the late 1960s, much less corrosive and more effective. It is rated for C fires. Along with sodium chloride and lithium chloride, potassium chloride is used as a flux for the gas welding of aluminium. Potassium chloride is an optical crystal with a wide transmission range from 210 nm to 20 µm. While cheap, KCl crystal is hygroscopic; this limits its application to short-term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were used for infrared optics, it has been replaced by much tougher crystals such as zinc selenide. Potassium chloride has been used to produce heat packs which employ exothermic chemical reactions, but these have been discontinued with the advent of cheaper and more efficient methods, such as the oxidation of metals or the crystallization of sodium acetate. Potassium chloride is used as a scotophor with designation P10 in dark-trace CRTs, e.g. in the Skiatron.
The typical amounts of potassium chloride found in the diet appear to be safe. In larger quantities, potassium chloride is toxic; the LD50 of orally ingested potassium chloride is 2.5 g/kg, or 190 grams for a body mass of 75 kilograms. In comparison, the LD50 of sodium chloride is 3.75 g/kg. Intravenously, the LD50 of potassium chloride is far smaller, at about 57.2 mg/kg to 66.7 mg/kg. In such quantities, it has severe consequences on the cardiac muscles causing cardiac arrest and rapid death. For this reason, it is used as the final drug delivered in the lethal injection process. KCl is soluble in a variety of polar solvents. Solutions of KCl are common standards, for example for calibration of the electrical conductivity of solutions, since KCl solutions are stable, allowing for reproducible measurements. In aqueous solution, it is fully ionized into solvated K+ and Cl– ions. Although potassium is more electropositive than sodium, KCl can be reduced to the metal by reaction with me
Methylidyne called carbyne, is an organic compound with the chemical formula CH•. Methylidyne is the simplest carbyne, it is a reactive gas, destroyed in ordinary conditions but is abundant in the interstellar medium. In October 2016, astronomers reported that the basic chemical ingredients of life – the carbon-hydrogen molecule, the carbon-hydrogen positive ion, the carbon ion – are the result of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovae and young stars, as thought earlier; these results have given new light to the formation of organic compounds in the early development of life on earth. The trivial name carbyne is the preferred IUPAC name; the systematic names methylidyne, hydridocarbon, valid IUPAC names, are constructed according to the substitutive and additive nomenclatures, respectively. Methylidyne is viewed as methane with three hydrogen atoms removed. By default, this name pays no regard to the radicality of methylidyne.
When the radicality is considered, the radical states with one unpaired electron are named methylylidene, whereas the radical excited states with three unpaired electrons are named methanetriyl. As an odd-electron species, CH is a radical; the ground state is a doublet. The first two excited states are a doublet; the quartet lies at 71 kJ above the ground state. Reactions of the doublet radical with non-radical species involves insertion or addition, whereas reactions of the quartet radical involves only abstraction. • + H2O → • + H2 or • 3• + H2O → + • Methylidyne-like species are implied intermediates in the Fischer–Tropsch process, the hydrogenation of CO into hydrocarbons. Methylidyne entities are assumed to bond to the catalyst's surface. A hypothetical sequence is: MnCO + 1/2 H2 → MnCOH MnCOH + H2 → MnCH + H2OA molecular example of an MnCH is HCCo39. MnCH + 1/2 H2 → MnCH2The methylene ligand is poised couple to CO or to another methylene, thereby growing the C–C chain; the methylylidyne group can exhibit both Lewis basic character.
Such behavior is only of theoretical interest. Methylidine can be prepared from bromoform. Methylene group Methylene bridge
Buckminsterfullerene is a type of fullerene with the formula C60. It has a cage-like fused-ring structure that resembles a football, made of twenty hexagons and twelve pentagons, with a carbon atom at each vertex of each polygon and a bond along each polygon edge, it was first generated in 1984 by Eric Rohlfing, Donald Cox and Andrew Kaldor using a laser to vaporize carbon in a supersonic helium beam. In 1985 their work was repeated by Harold Kroto, James R. Heath, Sean O'Brien, Robert Curl, Richard Smalley at Rice University, who recognized the structure of C60 as buckminsterfullerine. Kroto and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of buckminsterfullerene and the related class of molecules, the fullerenes. Buckminsterfullerene is the most common occurring fullerene, it can be found in small quantities in soot. The molecule has been detected in deep space; the discoverers of the allotrope named the newfound molecule after Buckminster Fuller, who designed many geodesic dome structures that look similar to C60.
This is misleading, however, as Fuller's geodesic domes are constructed only by further dividing hexagons or pentagons into triangles, which are deformed by moving vertices radially outward to fit the surface of a sphere. A common, shortened name for buckminsterfullerene is "buckyballs". Theoretical predictions of buckyball molecules appeared in the late 1960s and early 1970s, but these reports went unnoticed. In the early 1970s, the chemistry of unsaturated carbon configurations was studied by a group at the University of Sussex, led by Harry Kroto and David Walton. In the 1980s, Smalley and Curl at Rice University developed experimental technique to generate these substances, they used laser vaporization of a suitable target to produce clusters of atoms. Kroto realized. Concurrent but unconnected to the Kroto-Smalley work, astrophysicists were working with spectroscopists to study infrared emissions from giant red carbon stars. Smalley and team were able to use a laser vaporization technique to create carbon clusters which could emit infrared at the same wavelength as had been emitted by the red carbon star.
Hence, the inspiration came to Smalley and team to use the laser technique on graphite to generate fullerenes. C60 was discovered in 1985 by Robert Curl, Harold Kroto, Richard Smalley. Using laser evaporation of graphite they found Cn clusters of which the most common were C60 and C70. A solid rotating graphite disk was used as the surface from which carbon was vaporized using a laser beam creating hot plasma, passed through a stream of high-density helium gas; the carbon species were subsequently ionized resulting in the formation of clusters. Clusters ranged in molecular masses, but Kroto and Smalley found predominance in a C60 cluster that could be enhanced further by allowing the plasma to react longer, they discovered that the C60 molecule formed a cage-like structure, a regular truncated icosahedron. For this discovery Curl and Smalley were awarded the 1996 Nobel Prize in Chemistry; the experimental evidence, a strong peak at 720 atomic mass units, indicated that a carbon molecule with 60 carbon atoms was forming, but provided no structural information.
The research group concluded after reactivity experiments, that the most structure was a spheroidal molecule. The idea was rationalized as the basis of an icosahedral symmetry closed cage structure. Kroto mentioned geodesic dome structures of the noted futurist and inventor Buckminster Fuller as influences in the naming of this particular substance as buckminsterfullerene. In 1989 physicists Wolfgang Krätschmer, Konstantinos Fostiropoulos, Donald R. Huffman observed unusual optical absorptions in thin films of carbon dust; the soot had been generated by an arc-process between two graphite electrodes in a helium atmosphere where the electrode material evaporates and condenses forming soot in the quenching atmosphere. Among other features, the IR spectra of the soot showed four discrete bands in close agreement to those proposed for C60. Another paper on the characterization and verification of the molecular structure followed on in the same year from their thin film experiments, detailed the extraction of an evaporable as well as benzene soluble material from the arc-generated soot.
This extract had TEM and X-ray crystal analysis consistent with arrays of spherical C60 molecules 1.0 nm in van der Waals diameter as well as the expected molecular mass of 720 u for C60 in their mass spectra. The method was simple and efficient to prepare the material in gram amounts per day which has boosted the fullerene research and is today applied for the commercial production of fullerenes; the discovery of practical routes to C60 led to the exploration of a new field of chemistry involving the study of fullerenes. Soot is produced by pyrolysis of aromatic hydrocarbons. Fullerenes are extracted from the soot with organic solvents using a Soxhlet extractor; this step yields a solution containing up to 75% of C60, as well as other fullerenes. These fractions are separated using chromatography; the fullerenes are dissolved in a hydrocarbon or halogenated hydrocarbon and separated using alumina columns. Buckminsterfullerene is a truncated icosahedron with 60 vertices and 32 faces with a carbon atom at the vertices of each polygon and a bond along each polygon edge.
The van der Waals diameter of a C60 molecule is about 1.01 nanometers. The nucleus to nucleus diameter of a
Titanium oxide may refer to: Titanium dioxide, TiO2 Titanium oxide, TiO, a non-stoichiometric oxide Titanium oxide, Ti2O3 Ti3O Ti2O δ-TiOx TinO2n−1 where n ranges from 3–9 inclusive, e.g. Ti3O5, Ti4O7, etc. Used as an active ingredient in sunscreens combined with oxybenzone and octyl methoxycinnamate. Used in making of vehicle exhaust pipes due to its aesthetic value of the purple color