Fluorine is the chemical element with atomic number 9

Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of thehalogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic molecules, F2. Sony VAIO VGN-Z47GD/X Battery

In stars, fluorine is relatively rare compared to other light elements. On Earth, fluorine is more common; it is the 13th most abundant element in the crust.

Fluorine's most important mineral, fluorite, was first formally described in 1530, in the context of metal smelting.Sony VAIO VGN-Z48GD/X Battery

The mineral's name derives from the Latin verb fluo, which means "stream" or "flow," because fluorite was added to metal ores to lower their melting points. Suggested to be a chemical element in 1811, fluorine was named after the source mineral.Sony VAIO VGN-Z48TD/X Battery

It was not until 1886 that elemental fluorine was obtained by French chemist Henri Moissan, whose method of electrolysis remains the only industrial production method of fluorine gas. The main use of elemental fluorine, uranium enrichment, was developed during the Manhattan Project.Sony VAIO VGN-Z51WG/B Battery

However, the vast majority of commercial fluorine is never reduced to the element.

Fluorine has the highest electron affinity of any element but chlorine, and for this reason it is a very strong oxidizing agent. Fluorine forms stable compounds, fluorides, with all elements except helium and neon, for which the reaction has been attempted. Sony VAIO VGN-Z51XG/B Battery

Hydrofluoric acid, in contrast to other haloacids such as hydrochloric acid, is only a weak acid in water, but it is nonetheless extremely corrosive. Fluorides of lighter metal elements are ionic compounds (salts), which are usually watersoluble. Heavier metal elements such as uranium can form volatile coordination compounds (separate molecules with several fluorine atoms surrounding a metal atom). Sony VAIO VGN-Z530N/B Battery

Organic fluorine compounds tend to have high chemical and thermal stability and water-repellent properties. Several have large-scale commercial application, such as the fluorinated plasticpolytetrafluoroethylene ("Teflon") used in cookware. Another major application is fluorinated refrigerants.Sony VAIO VGN-Z540EBB Battery

Here, traditional chlorofluorocarbons ("Freons"), which cause ozone depletion, have been largely replaced by hydrofluorocarbons.

Although it helps prevent tooth decay, fluorine is not an essential mineral for mammals. Some organofluorine compounds are synthesized in microorganisms and plants. Several fluorine compounds, as well as elemental fluorine itself, are dangerously toxic.Sony VAIO VGN-Z540NLB Battery

Nevertheless, an increasing number of pharmaceuticals (about 10% of new drugs) contain fluorine.

Electronic structure

A fluorine atom has nine protons and thus nine electrons, arranged in electronic configuration [He]2s22p5, one fewer thanneon.Sony VAIO VGN-Z540NMB Battery

Fluorine's outer electrons are relatively separate from each other, and do not shield each other from the nucleus. Therefore, they experience a relatively high effective nuclear charge of +7. Fluorine tightly holds its own electrons and has an attraction for one more electron to achieve the extremely stable neon-like arrangement.Sony VAIO VGN-Z550N/B Battery

Fluorine's first ionization energy (energy required to remove an electron to form F+) is 1,681 kilojoules per mole, which is higher than for any other element except neon and helium. The second and third ionization energies of fluorine are 3,374 and 6,147 kilojoules per mole, respectively.Sony VAIO VGN-Z55F Battery

Fluorine's electron affinity (energy released by adding an electron to form F–) is 328 kilojoules per mole, which is higher than that of any other element except chlorine. Fluorine has a relatively small covalent radius, on average about 60 picometers, which slightly exceeds the numbers of neon but is surpassed by those of oxygen.Sony VAIO VGN-Z55TG/B Battery

Isotopes

Fluorine occurs naturally on Earth exclusively in the form of its only stable isotope, fluorine-19, which makes the element both monoisotopic and mononuclidic. In total, at least 17 radioisotopes have been synthesized, ranging in mass number from 14 to 31.Sony VAIO VGN-Z56GG/B Battery

Fluorine-18 is the most stable radioisotope of fluorine, with a half-life of 109.77 minutes, and the lightest unstable nuclide with equal odd numbers of protons and neutrons. All isotopes heavier than the stable fluorine-19 decay via beta minus decay (electron emission), for some isotopes possibly together with neutron emission.Sony VAIO VGN-Z56GG/E Battery

Isotopes lighter than the stable fluorine-19 undergo electron capture, while fluorine-17 and fluorine-18 decay via beta plus decay (positron emission).

Only one nuclear isomer, fluorine-18m, has been characterized. Its half-life before gamma ray emission is approximately 160 nanoseconds, which is less than that of the ground states of the isotopes from fluorine-17 to fluorine-30, except for fluorine-28.Sony VAIO VGN-Z56GGX Battery

Description

Fluorine atoms form diatomic molecules that are gaseous at room temperature. The density is 1.696 grams per liter at 100 kilopascal and 0 °C, about 1.3 times as dense as air. Though sometimes cited as yellow-green, fluorine gas is a very pale yellow. Sony VAIO VGN-Z56TG/B Battery

Its color can only be observed in concentrated fluorine gas when looking down the axis of long tubes. It appears transparent when observed from the side in normal glass tubes or if allowed to escape into the atmosphere.The element has a "pungent" characteristic odor that is noticeable in concentrations as low as 20 ppb.Sony VAIO VGN-Z56TG/E Battery

Fluorine condenses to a bright yellow liquid at ?188.1 °C (?306.6 °F), a comparable temperature to the boiling points of oxygen and nitrogen. Fluorine solidifies at ?219.6 °C (?363.3 °F) into a cubic structure, called beta-fluorine. Thisphase is transparent and soft, with significant disorder of the molecules. Sony VAIO VGN-Z56TG/R Battery

At ?227.5 °C (?377.5 °F) fluorine undergoes a solid–solid phase transition into a monoclinic structure called alpha-fluorine. This phase is opaque and hard with close-packed layers of molecules. The solid state phase change requires more energy than the melting point transition and can be violent, shattering samples and blowing out sample holder windows. Sony VAIO VGN-Z570N/B Battery

In general, fluorine's solid state is more similar to oxygen than the other halogens.

Chemical reactivity

Fluorine's chemistry is dominated by its tendency to gain an electron. It is the most electronegative element.Sony VAIO VGN-Z57G Battery

The removal of an electron from a fluorine atom requires so much energy that no known oxidant can oxidize fluorine to any positive oxidation state.

The high direct reactivity of fluorine gas results from the relative weakness of the fluorine–fluorine bond in elemental fluorine.Sony VAIO VGN-Z57GG/X Battery

The bond energy is similar to the easily cleaved oxygen–oxygen bonds of peroxides or nitrogen–nitrogen bonds of hydrazines and significantly weaker than those of dichlorine or dibromine molecules. The covalent radius of fluorine in difluorine molecules, about 71 picometers, is significantly larger than that in other compounds because of the weak bonding between fluorine atoms.Sony VAIO VGN-Z57GGX Battery

Reactions between fluorine and other elements are often sudden or explosive. Fluorine is so reactive that water, halogens, and most other substances, even generally nonreactive ones such as radon, burn with a bright flame in a jet of fluorine gas. It can even oxidize elemental nitrogen, Sony VAIO VGN-Z57TG/X Battery

which is extremely nonreactive due to its triple bonds, to give nitrogen trifluoride, though this occurs only when activated by electric discharge.

All metals react with fluorine to form fluorides, but different conditions are required for the reaction depending on the metal.Sony VAIO VGN-Z58GG/X Battery

Most frequently, the metals must be in powder forms, because many metals form layers of fluoride on their surfaces that resist further oxidation. Alkali metals react with fluorine violently and form fluorides with formula MF; alkaline earth metals react at room temperature as well, but such reactions are not so exothermic. Sony VAIO VGN-Z58GGX Battery

The metals ruthenium, rhodium, palladium, platinum andgold react least readily with fluorine, and are oxidized by the halogen only in atmospheres of pure fluorine at temperatures of 300–450 °C (575–850 °F). Fluorine reacts explosively with hydrogen in a manner similar to that of alkali metals.Sony VAIO VGN-Z590NJB Battery

Fluorine is known to form compounds with all elements up to einsteinium, element 99,except for helium, neon, astatine and francium; it is also known to form compounds with rutherfordium, element 104, and seaborgium, element 106. No attempt has been made to oxidize astatine, Sony VAIO VGN-Z590UAB Battery

francium, four later actinides, dubniumor any elements above seaborgium with fluorine, due to the radioactive instability of these elements, though such oxidations are possible in theory. Computational studies have suggested that helium could form a bond with fluorine,Sony VAIO VGN-Z591U/B Battery

and excited states containing neon–fluorine bonds have been observed in a mixture of neon and fluorine irradiated with electrons.Argon reacts with hydrogen fluoride to form argon fluorohydride at low temperatures.

Origin and occurrence

From the perspective of cosmology, fluorine is relatively rare with 400 ppb in the universe because of its tendency to undergo nuclear fusion with hydrogen to form oxygen and helium,Sony VAIO VGN-Z59G Battery

or with helium to become neon and hydrogen, at solar coretemperatures. Most fluorine forms either in Type II supernovae when a neutrino hits an atom of neon, in asymptotic giant branch stars, or in blue Wolf-Rayet stars with masses over 40 solar masses (in which stellar winds blow the fluorine out of the star before hydrogen or helium can destroy it).Sony VAIO VGN-Z620D Battery

Even though fluorine, due to its chemical activity, does not exist in its elementary state on Earth, it can be found in the interstellar medium, and fluorine cations exist in stars and planetary nebulae.

Fluorine is the thirteenth most common element in Earth's crust, making up between 600 and 700 ppm of the crust by mass.Sony VAIO VGN-Z620N/B Battery

Three minerals exist on earth that contain enough fluorine to be mined and used as industrial resources.The most important is fluorite, which is used in smelting, construction, and the manufacture of hydrogen fluoride. Fluorapatiteis mined along with other apatites for its phosphate content, and is used mostly for production of phosphate fertilizers. Sony VAIO VGN-Z650N/B Battery

The hexafluorosilicates produced as by-product phosphoric acid are mostly disposed of as waste. Cryolite is the least abundant of the three and is directly used for the production of aluminium. The latter two minerals originate from meteoric water; cryolite has also been found in magmatic water.Sony VAIO VGN-Z670N/B Battery

Fluorocarbon-containingchlorofluorocarbons and tetrafluoromethane have been reported in rocks, presumably having formed without action of living organisms. They are not a commercially or environmentally important source of fluorine.

History

"Fluorine" is a word that ultimately derives from the Latin verb fluo, meaning "flow." Sony VAIO VGN-Z690CTO Battery

The mineral fluorite, a natural form of calcium fluoride, was first mentioned in 1529 by Georgius Agricola, who named it after its use as a "flux"—an additive that helps melt ores and slags during smelting. Agricola first named the mineral "fluorspar" as a latinization of the German Flußspat. Since then, the mineral has been renamed "fluorite," although "fluorspar" is still sometimes used.Sony VAIO VGN-Z690NAX Battery

Andreas Sigismund Marggraf made the first recorded preparation of "fluoric acid" (hydrofluoric acid in modern nomenclature) in 1764, when he heated fluorite with sulfuric acid in glass, which was greatly corroded by the product. In 1771, Swedish chemist Carl Wilhelm Scheele repeated this reaction.Sony VAIO VGN-Z690PAB Battery

In 1810, French physicist André-Marie Ampère suggested that the acid was a compound of hydrogen with an unknown element, analogous to chlorine; Fluorite was then shown to be mostly composed of calcium fluoride. Sir Humphry Davyoriginally suggested the name fluorine, taking the root from the name of "fluoric acid" and the -ine suffix, similarly to other halogens;Sony VAIO VGN-Z690PCB Battery

this name, with modifications, came to most European languages. Greek, Russian, and several other languages use the ftor or deratives, which comes from Greek ???????, meaning "destructive." The new Latin name (fluorum) gave the element its current symbol F, although the symbol Fl is seen in pre-Moissan papers.Sony VAIO VGN-Z690PDB Battery

Owing to its extreme reactivity, elemental fluorine was not isolated until many years after the characterization of fluorite. Progress in isolating elemental fluorine was slow because it could only be prepared electrolytically and even then under stringent conditions, since the gas reacts with most materials. Sony VAIO VGN-Z690PEB Battery

The generation of elemental fluorine from hydrofluoric acid proved to be exceptionally dangerous, killing or blinding several people who attempted early experiments on this halogen. Jean Dussaud referred to these scientists as "fluorine martyrs," a term still used.Sony VAIO VGN-Z690PFB Battery

In 1886, French chemist Henri Moissan reported the isolation of elemental fluorine, after almost 74 years of effort by other chemists.Moissan received the 1906 Nobel Prize in chemistry for the feat.

The two most prominent developments of organofluorine compounds are chlorofluorocarbon refrigerants such as Freon-12, and Teflon. Both were associated with theDuPont company.Sony VAIO VGN-Z690YAD Battery

Chlorofluorocarbons are now being replaced by hydrofluorocarbons.

Large-scale productions of elemental fluorine began during World War II. Germany used high-temperature electrolysis to produce tons of chlorine trifluoride, a compound planned to be used as an incendiary.Sony VAIO VGN-Z691Y/B Battery

The Manhattan project in the United States produced even more fluorine for use in uranium separation. Gaseous uranium hexafluoride, was used to separate uranium-235, an important nuclear explosive, from the heavier uranium-238 in centrifuges and diffusion plants.Sony VAIO VGN-Z691Y/X Battery

Because uranium hexafluoride releases small quantities of corrosive fluorine, the separation plants were built with special materials. All pipes were coated with nickel, which forms a protective fluoride layer on its surface after exposure to fluorine. Joints and flexible parts were fabricated from Teflon.Sony VAIO VGN-Z698Y/X Battery

Production

Industrially, fluorine is used either directly as the mined mineral fluorite or as hydrogen fluoride (obtained from the reaction of sulfuric acid with fluorite). Only a very small fraction of industrial fluorine is ever electrolyzed to molecular fluorine, F2. Most fluorine in synthesized organofluorines derives from hydrogen fluoride, not molecular fluorine.Sony VAIO VGN-Z699JAB Battery

Electrolytic synthesis

Several thousand tons of elemental fluorine are produced annually by electrolysis of potassium bifluoride in hydrogen fluoride.Potassium bifluoride forms spontaneously from potassium fluoride and the hydrogen fluoride:

HF + KF ? KHF2 Sony VAIO VGN-Z70B Battery

A mixture with the approximate composition KF•2HF melts at 70 °C (158 °F) and is electrolyzed between 70 °C and 130 °C (160–265 °F). Potassium bifluoride increases the electrical conductivity of the solution and provides the bifluoride anion, which is oxidized to form fluorine at the anode. Sony VAIO VGN-Z71JB Battery

When HF is electrolyzed, hydrogen forms at the cathode and the fluoride ions remain in solution. After electrolysis, potassium fluoride remains in solution.

2 HF2– ? H2? + F2? + 2 F–

Henri Moissan first pioneered this method of electrolysis. Moissan used platinum group metal electrodes and carved fluorite containers, Sony VAIO VGN-Z73FB Battery

but the modern process uses the steel cells that act as cathodes, while blocks of carbon are used as anodes (the Söderberg carbon electrodes are similar to those used in the electrolysis of aluminium). The voltage for the electrolysis varies between 8 and 12 volts.Sony VAIO VGN-Z790DKX Battery

Pure fluorine gas may be stored in steel cylinders, where the inside surface becomes passivated by a metal fluoride layer that resists further attack.

Chemical routes

In 1986, when preparing for a conference to celebrate the 100th anniversary of the discovery of fluorine, Karl Christe discovered a purely chemical preparation of fluorine gas.Sony VAIO VGN-Z790DMR Battery

It involved the reaction of potassium hexafluoromanganate and antimony pentafluoride at 150 °C, in an atmosphere of hydrogen fluoride:

2 K2MnF6 + 4 SbF5 ? 4 KSbF6 + 2 MnF3 + F2?

This synthetic route is a rare chemical preparation of elemental fluorine, a reaction not previously thought possible.Sony VAIO VGN-Z790DND Battery

The manganese(IV) fluoride has to be prepared by reaction with fluorine gas itself, or with krypton difluoride, which is synthesized by reaction with elemental fluorine. This reaction is therefore not an industrially viable way to produce fluorine. Fluorine can by synthesized by the reaction of hexafluoronickelate ion NiF2?6 with the fluorides of the heavier noble gases (krypton and xenon ), which can only be produced by a reaction of krypton or xenon with fluorine gas.Sony VAIO VGN-Z820DB Battery

Economic aspects

With the exception of countries with planned economics, about 17,000 tonnes of fluorine are produced per year by 11 companies in G7 countries. Fluorine is relatively inexpensive, costing about $5–8 per kilogram when sold as uranium hexafluoride or sulfur hexafluoride. Sony VAIO VGN-Z820G/B Battery

Because of difficulties in storage and handling, the price of pure fluorine gas is much higher.

Compounds

Fluorine exists in the ?1 oxidation state in all compounds except for elemental fluorine, where the atoms are bonded to each other and thus at oxidation state 0. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Sony VAIO VGN-Z890GLX Battery

Most frequently, covalent bonds involving fluorine atoms are single bonds. Higher bonding can occur, for example boron monofluoride features a triple bond.Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding.Sony VAIO VGN-Z890GMR Battery

Inorganic acids

Unlike other hydrohalic acids, such as hydrochloric acid, hydrofluoric acid is only a weak acid in water solution, with acid dissociation constant (pKa) equal to 3.18. The acid's weak acidity in water is due to the hydrogen bonding between the fluoride and hydronium ions and the decrease in entropy that occur when hydrofluoric acid dissociates.Sony VAIO VGN-Z898H/X Battery

When less basic solvents such as dry acetic acid are used, hydrofluoric acid is the strongest of the hydrohalic acids. Despite its weakness as an acid in water, hydrogen fluoride is very corrosive, attacking glass. Due to the basicity of the fluoride ion, soluble fluorides give basic water solutions.Sony VAIO VGN-Z90FS Battery

Perfluoroacids, which are acids that contain only hydrogen, fluorine and atoms of one other element in the center of the acid's anion, are generally very strong. Fluoroantimonic acid, one such acid, is a "superacid" and the strongest acid known. It has an extremely low pKa of ?31.3 and is 20 quintillion (2×1019) times stronger than pure sulfuric acid, which has pKa of ?12.Sony VAIO VGN-Z90NS Battery

This happens because fluorine atoms are univalent and thus cannot form strong chemical bonds to both the antimony atom and thehydron. By occupying all antimony's valence electrons, fluorine atoms prevent the hydron from bonding to it.

Metal fluorides

Metal fluorides have similarities to other metal halides and to metal oxides, but the ionic character is stronger in metal fluorides than in the corresponding chlorides or oxides. Sony VAIO VGN-Z90PS Battery

The solubity of ionic fluorides varies greatly, but tends to decrease as the number of fluorides increases. Alkali metal fluorides often resemble the chlorides in terms of structure (all having the sodium chloride structure) and solubilities. Because the fluoride anion is highly basic, many alkali metal fluorides form bifluorides with the formula MHF2; Sony VAIO VGN-Z90S Battery

this is a well-known process for sodium and potassium in chemical industry. Among other monofluorides, only silver(I) and thallium(I) fluorides are well-characterized; both are very soluble, unlike other corresponding halides. Unlike the chlorides, alkaline earth metals (except for beryllium) form fluorides that are only sparingly soluble.Sony VAIO VGN-Z90US Battery

Several other difluorides, such as those of copper(II) and nickel(II), are soluble. No trifluoride is soluble in water, but several may be soluble in other solvents.

While metal tri- and lower fluorides are ionic solids, metal penta- and higher fluorides are molecular and volatile. Sony VAIO VGN-Z91DS Battery

Tetrafluorides are the borderline: for example,zirconium tetrafluoride is an ionic solid, but germanium tetrafluoride is a molecular gas. This property of the fluoride ion is partially caused by its small radius. Only rhenium is known to form bonds with seven fluorides, forming rhenium heptafluoride, which holds the record for number of charged ligands for a metal compound. Sony VAIO VGN-Z91JS Battery

The compounds shares the pentagonal bipyramid molecular geometry with iodine heptafluoride, the only well-studied analogous nonmetal compound. Metal hexafluorides and higher fluorides are oxidants: for example, platinum hexafluoride was the first compound to oxidize molecular oxygen and xenon (see below). Sony VAIO VGN-Z91PS Battery

Metal fluorides can be volatile solids, liquids, or gases at room temperature.

Nonmetal fluorides

The nonmetal fluorides are volatile. Period 2 elements form fluorides that follow the octet rule: carbon tetrafluoride, nitrogen trifluoride, andoxygen difluoride.Sony VAIO VGN-Z91YS Battery

The only exception from this is boron trifluoride, which has only six electrons around the central boron atom (and thus an incomplete octet). This explains the great acidic potential of the compound: in order to complete the octet, it attracts Lewis bases such as ammonia or another fluoride ion.Sony VAIO VGN-Z92DS Battery

Lower periods, however, may form fluorides that are hypervalent molecules, such as phosphorus pentafluoride. The reactivity of such species varies greatly: sulfur hexafluoride is inert, while chlorine fluorides are oxidants.

Boron trifluoride forms planar molecules and is notable for being a Lewis acid.Sony VAIO VGN-Z92JS Battery

Silicon tetrafluoride is a weaker acid and less thermally stable, but carbon tetrafluoride is relatively chemically stable. Among pnictogens (nitrogen and the elements directly under it in the periodic table), reactivity and acidity of fluorides increases down the group, but bismuth is an exception: Sony VAIO VGN-Z92PS Battery

bismuth pentafluoride is not as acidic as antimony pentafluoride because it is polymeric and its trifluoride is ionic. Nitrogen is another special case in that it is not known to form a pentafluoride, although tetrafluoroammonium ion, NF+
4, with nitrogen in the formal oxidation state of +5, is known.Sony VAIO VGN-Z92YS Battery

Chalcogens (oxygen and its direct lower periodic table neighbors) show analagous characteristics: hexafluorides increase in acidity and reactivity down the group; oxygen is not known to be oxidized above difluoride. In halogens, unlike previous groups, not all elements form fluorides of their highest oxidation states. Sony VAIO VGN-Z93FS Battery

Chlorine and bromine form pentafluorides, both strong fluorinators; iodine may be oxidized up to iodine heptafluoride. Astatine is not well-studied, and astatine fluoride has not been produced, even though this should be possible.

Noble gas compounds

The noble gases are generally non-reactive because they all have fully filled electronic shells, which are extremely stable. Sony VAIO VGN-Z93GS Battery

The ability of fluorine-containing platinum hexafluoride to react with xenon was first reported by Neil Bartlett in 1962. He called the compound he prepared xenon hexafluoroplatinate, but since then the product has been revealed to be mixture of different chemicals. Sony VAIO VGN-Z93HS Battery

Later that year, xenon was oxidized directly with fluorine, to form xenon difluoride. Today, only xenon and krypton have well-characterized binary noble gas–fluorine compounds, which include xenon difluoride, krypton difluoride, xenon tetrafluoride, krypton tetrafluoride, xenon hexafluoride and their deratives.Sony VAIO VGN-Z93VS Battery

Several oxyfluorides and oxyfluoroxenates are known, including xenon oxytetrafluoride, XeOF4.

Radon readily reacts with fluorine to form a solid compound, which is generally thought to be radon difluoride; however, its exact composition is uncertain. Calculations indicate that radon difluoride can be ionic, unlike all other binary noble gas fluorides.Sony A1258274A Battery

Argon can react in extreme conditions with hydrogen fluoride, to form its only stable compound—argon fluoride hydride. Helium can form an analogous helium fluoride hydride but it is metastable, with a lifetime of at most 14 nanoseconds.Argon forms binary argon monofluoride, ArF•, which, because of its metastability, is used in the argon fluoride laser.Sony VGP-BPL10 Battery

Even though the reactivity of neon is the lowest of all the elements, the element forms a metastable chemical compound, neon monofluoride, NeF•.

Ununoctium, the last currently known group 18 element, is predicted to form ununoctium difluoride, UuoF2, and ununoctium tetrafluoride, UuoF4, which is likely to have the tetrahedral Td configuration.Sony VGP-BPS10 Battery

However, only a few atoms of ununoctium have been synthesized, and its chemical properties have not been examined yet (as of 2011).

Highest oxidation states

Elements frequently have their highest oxidation state in the form of a binary fluoride. Sony VGP-BPS10/S Battery

Several elements show their highest oxidation state only in a few compounds, one of which is the fluoride; and some elements' highest known oxidation state is seen exclusively in a fluoride.

Fluorine was the first element able to oxidize a group 12 element to an oxidation state above +2; making the element's d-electrons participate in bonding.Sony VGP-BPS10A/B Battery

Mercury(IV) fluoride was produced by this reaction, the first ever mercury(IV) compound; its discovery has heated the debate over whether mercury, cadmium, and zinc are transition metals.Another unique oxidation state available for fluorine only is gold(V).Sony VGP-BPS10B Battery

It is only known in the hexafluoroaurate(V) ion, which can be synthesized indirectly under extreme conditions, and gold(V) fluoride, which is obtained during hexafluoroaurate(V) decomposition. Because of fluorine's high oxidizing potential it was suggested that gold heptafluoride contained gold(VII), but current calculations show that the claimed AuF7 molecule was AuF5·F2.Sony VGP-BPS10A Battery

Aside from these examples, fluorine is the only element that is known to oxidize the respective elements to palladium(VI), platinum(VI), copper(IV), silver(IV), nickel(IV), iridium(VI), and krypton(II). It is possible that element 113, ununtrium, will be the first boron group element to form a species in the +5 oxidation state, the fluorine-based hexafluoroununtrate(V), UutF?6; no other ununtrium(V) species is expected.Sony VGP-BPS11 Battery

Comparison between the highest oxidation states of oxides and fluorides

For groups 1—6, 13, 14, and 16 the highest oxidation states of oxides and fluorides are always equal, and differences are only seen in groups 7—11, mercury, nitrogen, halogens, and the noble gases.Sony VGP-BPL11 Battery

Fluorination allows elements to achieve relatively low oxidation states that are, however, hard to achieve; for example, no binary oxide is known for krypton, but krypton difluoride is well-studied. At the same time, very high oxidation states are known for oxygen-based species only;Sony VGP-BPL12 Battery

for example, ruthenium octafluoride has not been synthesized, while ruthenium tetroxide is well-studied.The main problem that prevents fluorine from forming the highest states in covalent hepta- and octafluorides is that it is hard to attach such a large number of ligands around a single atom; the number of ligands is halved in analogous oxides.Sony VGP-BPS12 Battery

Organic compounds

Organofluorine compounds are chemical compounds that contain a carbon–fluorine chemical bond. This bond is the strongest covalent bond in organic chemistry and is very stable. Fluorine replaces hydrogen in hydrocarbons even at room temperature; after the reaction, the molecular size is not changed significantly.Sony VGP-BPL13 Battery

The range of organofluorine compounds is thus diverse; consequently, the research in the area and its uses are driven by the commercial value of such compounds in materials science and pharmaceutical chemistry. Organofluorine compounds are synthesized via both direct reaction with fluorine gas, which can be dangerously reactive, or reaction with fluorinating reagents such as sulfur tetrafluoride.Sony VGP-BPS13 Battery

The most industrially important compounds of fluorine include Polytetrafluoroethylene (also called PTFE or Teflon) and hydrofluorocarbons, the main properties of which are affected by the carbon–fluorine bonds in them. The slippery nature of PTFE is the result of chemical stability and repulsion of highly charged fluorine atoms in polymeric chains. Sony VGP-BPS13/B Battery

Its resistance to van der Waals forces makes PTFE the only known surface to which a gecko cannot stick. Properties of the chlorofluorocarbons and hydrochlorofluorocarbons depend on the number and identity of the halogen atoms. Sony VGP-BPS13/S Battery

The volatility of these compounds is lower than in most organic compounds because of the strength of the carbon–fluorine bond and carbon–chlorine bond, as well as the molecular polarity induced by the halides and the polarity of halides themselves, which cause intermolecular interactions. Sony VGP-BPS13/S Battery

The large difference between chlorine and fluorine atomic radii makes chlorofluorocarbons asymmetric, which increases the polarity in the molecules; these effects lead to high solubility potential and higher boiling points of chlorofluorocarbons compared to those of parent hydrocarbons.Sony VGP-BPS13A/B Battery

Chlorofluorocarbons are far less flammable than methane, in part because they contain fewer carbon–hydrogen bonds and in part because the released halides quench the free radicals that sustain flames.

The large inductive effect of the trifluoromethyl group results in the high acid strength of many fluorinated organic acids, which may be comparable to mineral acids.Sony VGP-BPS13A/S Battery

In these compounds, the cation's affinity for the acid proton is decreased by the cation's fluorine content, which increases its affinity for the extra electron left when the acidic proton leaves. For example, acetic acid is a weak acid, with pKa equal to 4.76, while its fluorinated derivative, trifluoroacetic acidhas pKa of ?0.23, giving it 33,000 times greater formal acidic potential.Sony VGP-BPS13AS Battery

Applications

Approximately half of mined fluorite is used to help molten metal flow, especially in iron smelting. The other half is converted to hydrofluoric acid, which is mostly used to produce organofluorides or synthetic cryolite.Sony VGP-BPS13B/B Battery

Uses of fluorine gas

Elemental fluorine is occasionally used as a fluorinating agent in industrial processes. The largest application for elemental fluorine is preparation of uranium hexafluoride, used in the production of nuclear fuels. To obtain the compound, uranium dioxide is treated with hydrofluoric acid, to produce uranium tetrafluoride, which is oxidized by fluorine to give uranium hexafluoride.Sony VGP-BPS13B/Q Battery

The second largest application for fluorine gas is sulfur hexafluoride, which is used as an inert dielectric medium in high voltage switching. Sulfur hexafluoride may be produced without using fluorine gas, but the reaction between pure sulfur and pure fluorine gas is the most commonly used in industry.Sony VGP-BPS13B/S Battery

Elemental fluorine is used for production of tetrafluoromethane,which is utilized for plasma etching in semiconductor manufacturing,flat panel displayproduction, and microelectromechanical systems fabrication. These and other require up to 2,000 tonnes annually.Sony VGP-BPS13Q Battery

United States and Soviet space scientists in the early 1960s studied elemental fluorine as a possible rocket propellant, due to its exceptionally high specific impulse when used as an oxidizer. The experiments failed because fluorine proved difficult to handle, and its combustion product (typically hydrogen fluoride) was extremely toxic and corrosive.Sony VGP-BPS13S Battery

Isotope applications

Natural fluorine is monoisotopic, consisting solely of fluorine-19. Fluorine compounds are highly amenable to nuclear magnetic resonance, because fluorine-19 has a nuclear spin of ½, a high nuclear magnetic moment, and a high magnetogyric ratio, which allows it to make measurements quickly, comparable with a similar effect based on hydrogen-1.Sony VGP-BPL7 Battery

Although it is not one of basic NMR active nuclei used in science and medicine, fluorine-19 is still commonly used in nuclear magnetic resonance, especially in the study of protein structures and conformational changes. Natural fluorine's monoisotopic occurrence makes it useful in uranium enrichment,Sony VGP-BPS7 Battery

because uranium hexafluoride molecules differ in mass only due to mass differences between uranium-235 and uranium-238. These mass differences are used to separate uranium-235 and uranium-238 via diffusion and gas centrifugation.

Compounds containing fluorine-18, a radioactive isotope that emits positrons, are often used in PET scanning, because its half-life of about 110 minutes is long by the standards of positron-emitters.Sony VGP-BPL8 Battery

One such species is 2-deoxy-2-(18F)fluoro-D-glucose, commonly abbreviated as 18F-FDG. In PET imaging, 18F-FDG can be used for the assessment of glucose metabolism in the brain and for imaging tumors in oncology. This radiopharmaceutical is retained by cells and is taken up by tissues with a high need for glucose, such as the brain and most types of malignant tumors.Sony VGP-BPL8A Battery

Tomography can thus be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin's disease, lung cancer, breast cancer, and many others.

Uses of compounds

Inorganic fluorides and organofluorine compounds find use in a variety of materials and chemicals, including important pharmaceuticals, agrochemicals, lubricants, and textiles.Sony VGP-BPL8B Battery

Hydrofluoric acid and certain fluoride-containing salts are useful for etching glass, light bulbs. Laboratory-produced sodium hexafluoroaluminate, better known as synthetic cryolite, the mineral composed mostly out of this chemical, is used in the electrolysis of aluminium and its purification metallurgy to lower the melting point of aluminium oxide; the compounds also act as a powerful flux for glass.Sony VGP-BPS8 Battery

Perfluorooctanoic acid and tetrafluoroethylene are used in water resistant coatings and in the production of low friction plastics such as PTFE, or Teflon. The lowvan der Waals forces in solid Teflon give it unusual antiadhesive properties. Nafion, a strongly acidic fluorinated polymer, is a component of fuel cells.Sony VGP-BPS8A Battery

Other fluorine-based compounds were once heavily used in the production of haloalkanes such as chlorofluorocarbons, which are used extensively in air conditioningand in refrigeration. CFCs have been banned for these applications because they contribute to ozone destruction,Sony VGP-BPS8B Battery

and have therefore been partly replaced withhydrofluorocarbons that contain no halogen other than fluorine, such as 1,1,1,2-tetrafluoroethane and 2,3,3,3-tetrafluoropropene. Another haloalkane,bromotrifluoromethane ("Halon") is still widely used in ship and aircraft gaseous fire suppression systems. Sony VGP-BPL9 Battery

Because Halon production has been banned since 1994, systems are dependent on the pre-ban stores and on recycling.

Living organisms

Fluoride is not considered an essential mineral element for mammals and humans, though its role in prevention of tooth decay is well-established.Sony VGP-BPS9 Battery

Sodium fluoride, tin(II) fluoride, and, most commonly, sodium monofluorophosphate, are used in toothpaste. These or related compounds, such as fluorosilicates, are added to many municipal water supplies, a process called water fluoridation, which has been controversial since its inception in 1945.Sony VGP-BPS9/B Battery

Small amounts of fluoride may be beneficial for bone strength, but this is an issue only in the formulation of artificial diets.

Biologically synthesized organofluorines have been found in microorganisms and plants, but not in animals. The most common example is fluoroacetate, which is used as a defense against herbivores by at least 40 plants in Australia, Brazil and Africa.Sony VGP-BPS9/S Battery

Other biologically synthesized organofluorines include ?-fluoro fatty acids, fluoroacetone, and 2-fluorocitrate, all of which are believed to be biosynthesized from the intermediate fluoroacetaldehyde. The enzyme adenosyl-fluoride synthase is capable of biologically synthesizing the carbon–fluorine bond.Sony VGP-BPS9A Battery

Pharmaceuticals, agricultural chemicals, and poisons

Several important pharmaceuticals contain fluorine. Because of the considerable stability of the carbon-fluorine bond, many drugs are fluorinated to prevent their metabolism and prolong their half-lives, allowing for longer times between dosing and activation.Sony VGP-BPS9A/B Battery

For example, an aromatic ring may add to prevent the metabolism of a drug, but this presents a safety problem, because enzymes in the body metabolize some aromatic compounds into poisonous epoxides. Substituting a fluorine into a para position, however, protects the aromatic ring and prevents the epoxide from being produced.Sony VGP-BPS9A/S Battery

Adding fluorine to biologically active organics increases theirlipophilicity, because the carbon–fluorine bond is even more hydrophobic than the carbon–hydrogen bond. This effect often increases a drug's bioavailability due to increased cell membrane penetration.Sony VGP-BPS9B Battery

Since the carbon–fluorine bond is strong, organofluorides are generally very stable, although the potential of the fluorine to be released as a fluoride leaving group is heavily dependent on the its position in the molecule.

Of drugs that have been commercialized in the past 50 years, 5–15% contain fluorine, and the percentage of currently available fluorine-containing drugs is increasing.Sony VGP-BPX11 Battery

For example, fludrocortisone is one of the most common mineralocorticoids, a class of drugs that mimics the actions of aldosterone. The anti-inflammatories dexamethasone and triamcinolone, which are among the most potent of the synthetic corticosteroids class of drugs, contain fluorine.Sony VGP-BPL18 Battery

Several inhaled general anesthetic agents, including the most commonly used inhaled agents, also contain fluorine. Examples include sevoflurane, desflurane, and isoflurane, which arehydrofluorocarbon derivatives.

Many SSRI antidepressants are fluorinated organics,including citalopram, escitalopram, fluoxetine, fluvoxamine, and paroxetine.Sony VGP-BPS18 Battery

Fluoroquinolones are a commonly used family of broad-spectrum antibiotics. Because biological systems do not metabolize fluorinated molecules easily, fluorinated pharmaceuticals (often antibiotics and antidepressants) are among the major fluorinated organics found in treated city sewage and wastewater.Sony VGP-BPL20 Battery

In addition to pharmaceuticals, an estimated 30% of agrochemical compounds contain fluorine. Because of these, water from agricultural sites contaminates rivers with runoff organofluorines. Synthetic sodium fluoroacetate has been used as an insecticide, especially against cockroaches, and is effective as a bait-poison against mammalian pests.Sony VGP-BPS20/B Battery

Several other insecticides contain sodium fluoride, which is much less toxic than fluoroacetate.

Chronology

Because groundwater contains fluorine ions, organic items such as bone that are buried in soil will absorb those ions over time. Sony VGP-BPS20/S Battery

As such, it is possible to determine the relative age of an object by comparing the amount of fluoride with another object found in the same area. It is important as a separation technique in intra-site chronological analysis and inter-site comparisons.

However, if no actual age of any object is known, the ages can only be expressed in terms of one of the objects being older or younger than the other. Sony VGP-BPL21 Battery

The fluctuating amount of fluoride found in groundwater means the objects being compared must be in the same local area in order for the comparisons to be accurate. This technique is not always reliable, given that not all objects absorb fluorine at the same rates.Sony VGP-BPS21 Battery

Environmental concerns

Chlorofluorocarbons and bromofluorocarbons have come under strict environmental regulation due to their long residence times in the atmosphere, and their contribution to ozone depletion. Sony VGP-BPS21/S Battery

Since it is specifically chlorine and bromine radicals that harm the ozone layer, not fluorine, compounds that do not contain chlorine or bromine but contain only fluorine, carbon, and hydrogen (called hydrofluorocarbons) are not on the United States Environmental Protection Agency list of ozone-depleting substances, and have been widely used as replacements for halocarbons containing chlorine and bromine.Sony VGP-BPS21A Battery

Hydrofluorocarbons and perfluorocarbons are greenhouse gases about 4,000 to 10,000 times as potent as carbon dioxide. Sulfur hexafluoride exhibits an even stronger effect, having 20,000 times the global warming potential of carbon dioxide.

Because of the strength of the carbon–fluorine bond, many synthetic fluorocarbons and fluorocarbon-based compounds are persistent in the environment. Sony VGP-BPS21A/B Battery

The fluorosurfactants perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), used in waterproofing sprays, and other related chemicals, are persistent global contaminants. PFOS is apersistent organic pollutant and may be harming the health of wildlife.Sony VGP-BPS21B Battery

The potential health effects of PFOA to humans are unclear; its tissue distribution in humans is unknown, but studies in rats suggest it is likely to be present primarily in the liver, kidney, and blood, as it is absorbed easily via the gastrointestinal tract in rats. PFOA has been shown not to metabolize in the body, and, unlike chlorinated hydrocarbons, it is neither genotoxic nor lipophilic.Sony VGP-BPL22 Battery

It binds to serum albumin and is excreted primarily from the kidney.

Elementary state, fluoride ion, and fluoroacetate

Elemental fluorine is a highly toxic, corrosive oxidant, and is extremely reactive to organic material (except for perfluorinated substances) even at very low concentrations and can cause ignition at higher ones.Sony VGP-BPS22 Battery

Significant irritation to humans can be caused by concentration of fluorine of 25 ppm; at this and higher concentrations fluorine attacks the eyes, respiratory tract, lungs, liver and kidneys. At a concentration of 100 ppm, human eyes and noses are irritated and seriously damaged.Sony VGP-BPS22/A Battery

Soluble fluorides are moderately toxic. In the case of the simple salt sodium fluoride, the lethal dose for most adult humans is estimated at 5 to 10 g, which is equivalent to 32 to 64 mg/kg elemental fluoride/kg body weight. A toxic dose that may lead to adverse health effects is estimated at 3 to 5 mg/kg of fluoride.Sony VGP-BPS22A Battery

The fluoride ion is somewhat toxic, in part because of its ability to form, by equilibration, small amounts of hydrogen fluoride in water. This mobile uncharged species diffuses across cell membranes to attack intracellular calcium. The fluoride ion is readily absorbed by the stomach, intestines and excretedthrough urine. Sony VGP-BPL23 Battery

Urine tests have been used to ascertain rates of excretion in order to set upper limits in exposure to fluoride compounds and associated detrimental health effects. Ingested fluoride initially acts locally on the intestinal mucosa, where it forms hydrofluoric acid in the stomach.Sony VGP-BPS23 Battery

Thereafter it binds with calcium and interferes with various enzymes. Excess fluoride consumption can lead to skeletal fluorosis, which currently affects millions of people.

Historically, most cases of fluoride poisoning have been caused by accidental ingestion of insecticides containing inorganic fluoride, or (more rarely)rodenticides containing sodium fluoroacetate ("Compound 1080").Sony VGP-BPS23/B Battery

Currently, most fluoride poisonings are due to the ingestion of fluoride-containing toothpaste. Malfunction of water fluoridation equipment has occurred several times, including an Alaskan incident, which affected nearly 300 people and killed one person. Sony VGP-BPS23/D Battery

Hydrofluoric acid

Hydrofluoric acid is a contact poison, and must be handled with extreme care far beyond that accorded to other mineral acids, even the analogous hydrochloric acid, HCl. Owing to its lesser chemical dissociation in water (remaining a neutral molecule), hydrogen fluoride penetrates tissue more quickly than typical acids. Sony VGP-BPS23/G Battery

Poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident. Hydrogen fluoride interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.Sony VGP-BPS23/P Battery

Once absorbed into blood through the skin, hydrogen fluoride reacts with blood calcium and may cause cardiac arrest. Formation of insoluble calcium fluoride possibly causes both a fall in calcium serum and the strong pain associated with tissue toxicity. In some cases, exposures can lead to hypocalcemia.Sony VGP-BPS23/W Battery

Burns with areas larger than 160 cm2 (25 in2) can cause serious systemic toxicity from interference with blood and tissue calcium levels.

Hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca2+ that binds with the fluoride ions. Sony Limited Edition 007 Battery

Hydrogen fluoride chemical burns to the skin can be treated with a water wash and 2.5% calcium gluconate gel or special rinsing solutions. However, because it is absorbed, medical treatment is necessary; in some cases, amputation may be required.

Caesium or cesium ( /?si?zi?m/ see-zee-?m) is the chemical element with the symbol Cs and atomic number 55.Sony VAIO VGC-LB15 Battery

It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at (or near) room temperature. Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium. Sony VGN-AR Series Battery

The metal is extremely reactive and pyrophoric, reacting with water even at ?116 °C (?177 °F). It is the least electronegative element that has stable isotopes, of which it has only one, caesium-133. Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, a fission product, are extracted from waste produced by nuclear reactors.Sony VGN-CR Series Battery

Two German chemists, Robert Bunsen and Gustav Kirchhoff, discovered caesium in 1860 by the newly developed method of flame spectroscopy. The first small-scale applications for caesium have been as a "getter" in vacuum tubes and in photoelectric cells. Sony VIAO VGN-G Series Battery

In 1967, a specific frequency from the emission spectrum of caesium-133 was chosen to be used in the definition of thesecond by the International System of Units. Since then, caesium has been widely used in atomic clocks.

Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids.Sony VIAO VGN-G118 Battery

It has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has ahalf-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Although the element is only mildly toxic, it is a hazardous material as a metal and its radioisotopes present a high health risk in case of radiation leaks.Sony VIAO VGN-G118CN/B Battery

Caesium is a very soft (it has the lowest Mohs hardness of all elements (0.2)), veryductile, silvery-white metal, which develops a silvery-gold hue in the presence of trace amounts of oxygen. It has a melting point of 28.4 °C (83.1 °F), making it one of the few elemental metals which are liquid near room temperature. Sony VIAO VGN-G118CN/T Battery

Mercury is the only elemental metal with a known melting point lower than caesium. In addition, the metal has a rather low boiling point, 641 °C (1,186 °F), the lowest of all metals other than mercury.Its compounds burn with a blue color.

Caesium forms alloys with the other alkali metals as well as with gold, and amalgams with mercury. Sony VIAO VGN-G218 Battery

At temperatures below 650 °C (1,202 °F), it alloys with cobalt, iron,molybdenum, nickel, platinum, tantalum or tungsten. It forms well-defined intermetallic compounds with antimony, gallium, indium and thorium, which are photosensitive. It mixes with the other alkali metals (except with lithium), and the alloy with a molardistribution of 41% caesium, Sony VGN-TZ121 Battery

47% potassium, and 12% sodium has the lowest melting point of any known metal alloy, at ?78 °C(?108 °F). A few amalgams have been studied: CsHg2 is black with a purple metallic lustre, while CsHg is golden-coloured, also with a metallic lustre.

Chemical properties

Caesium metal is highly reactive and very pyrophoric.Sony VGN-TZ13 Battery

In addition to igniting spontaneously in air, it reacts explosively with water even at low temperatures, more so than other members of the first group of the periodic table. The reaction with solid water occurs at temperatures as low as ?116 °C (?177 °F). Because of its high reactivity, the metal is classified as a hazardous material. Sony VGN-TZ131 Battery

It is stored and shipped in dry saturated hydrocarbons such as mineral oil. Similarly, it must be handled under inert atmosphere such as argon. It can be stored in vacuum-sealed borosilicate glass ampoules. In quantities of more than about 100 grams (3.5 oz), caesium is shipped in hermetically sealed stainless steel containers.Sony VGN-TZ132N Battery

The chemistry of caesium is similar to that of other alkali metals, but is more closely similar to that of rubidium, the element above caesium in the periodic table. Some small differences arise from the fact that it has a higher atomic mass and is moreelectropositive than other (non-radioactive) alkali metals.Sony VGN-TZ132/N Battery

Caesium is the most electropositive stable chemical element. The caesium ion is also larger and less "hard" than those of the lighter alkali metals.

Compounds

The vast majority of caesium compounds contain the element as the cation Cs+, which binds ionicallyto a wide variety of anions. One noteworthy exception is provided by the caeside anion (Cs?).Sony VGN-TZ17N Battery

Other exceptions include the several suboxides (see section on oxides below).

Returning to more normal compounds, salts of Cs+ are almost invariably colorless unless the anion itself is colored. Many of the simple salts are hygroscopic, but less so than the corresponding salts of the lighter alkali metals. The acetate, carbonate, halides, oxide, nitrate, and sulfatesalts are water-soluble. Sony VGN-TZ16N Battery

Double salts are often less soluble, and the low solubility of caesium aluminium sulfate is exploited in the purification of Cs from its ores. The double salt with antimony (such as CsSbCl4), bismuth, cadmium, copper, iron, and lead are also poorly soluble.

Caesium hydroxide (CsOH) is hygroscopic and a very strong base.Sony VGN-TZ18N Battery

It rapidly etches the surface ofsemiconductors such as silicon.CsOH has been previously regarded by chemists as the "strongest base", reflecting the relatively weak attraction between the large Cs+ ion and OH–.; it is indeed the strongest Arrhenius base, but a number of compounds that cannot exist in aqueous solution, such as n-butyllithiumand sodium amide,Sony VAIO VGN-AR47G/E1 Battery

are more basic.A stoichiometric mixture of caesium and gold will react to form caesium auride.

Complexes

Like all metal cations, Cs+ forms complexes with Lewis bases in solution. Because of its large size, Cs+ usually adopts coordination numbers greater than six-coordination, which is typical for the lighter alkali metal cations. Sony VAIO VGN-AR520E Battery

This trend is already apparent by the 8-coordination in CsCl, vs the halite motif adopted by the other alkali metal chlorides. Its high coordination number and softness (tendency to form covalent bonds) are the basis of the separation of Cs+ from other cations, as is practiced in the remediation of nuclear wastes, where 137Cs+ is separated from large amounts of non-radioactive K+.Sony VAIO VGN-AR53DB Battery

Halides

Caesium chloride (CsCl) crystallizes in the simple cubic crystal system. Also called the "caesium chloride structure", this structural motif is composed of aprimitive cubic lattice with a two-atom basis, each with an eightfold coordination; the chloride atoms lie upon the lattice points at the edges of the cube, while the caesium atoms lie in the holes in the center of the cubes. Sony VAIO VGN-AR54DB Battery

This structure is shared with CsBr and CsI, and many other compounds that do not contain Cs. In contrast, most other alkaline halides adopt the sodium chloride (NaCl) structure. The CsCl structure is preferred because Cs+ has an ionic radius of 174 pm andCl?181 pm.Sony VAIO VGN-AR550E Battery

Oxides

More so than the other alkali metals, caesium forms numerous binary compounds with oxygen. When caesium burns in air, the superoxide CsO2 is the main product. The "normal" caesium oxide (Cs2O) forms yellow-orange hexagonal crystals, and is the only oxide of the anti-CdCl2 type.Sony VAIO VGN-AR55DB Battery

It vaporizes at 250 °C (482 °F), and decomposes to caesium metal and the peroxide Cs2O2 at temperatures above 400 °C (752 °F). Aside from the superoxide and the ozonide CsO3, several brightly colored suboxides have also been studied. These include Cs7O, Cs4O, Cs11O3, Cs3O (dark-green ), CsO, Cs3O2, as well as Cs7O2.Sony VAIO VGN-AR630E Battery

The latter may be heated under vacuum to generate Cs2O. Binary compounds with sulfur,selenium, and tellurium also exist.

Isotopes

Caesium has a total of 39 known isotopes that range in their mass number (i.e. number of nucleons in its nucleus) from 112 to 151.Sony VAIO VGN-AR64DB Battery

Several of these are synthesized from lighter elements by the slow neutron capture process (S-process) inside old stars, as well as inside supernova explosions (R-process). However, the onlystable isotope is 133Cs, which has 78 neutrons. Although it has a large nuclear spin (7/2+), nuclear magnetic resonance studies can be done with this isotope at a resonating frequency of 11.7 MHz.Sony VAIO VGN-AR65DB Battery

The radioactive 135Cs has a very long half-life of about 2.3 million years, while 137Cs and 134Cs have half-lives of 30 and 2 years, respectively. 137Cs decomposes to a short-lived 137mBa by beta decay, and then to non-radioactive barium, while 134Cs transforms into 134Ba directly. Sony VAIO VGN-AR660U Battery

The isotopes with mass numbers of 129, 131, 132 and 136, have half-times between a day and two weeks, while most of the other isotopes have half-lives from a few seconds to fractions of a second. There are at least 21 metastable nuclear isomers. Other than 134mCs (with a half-life of just under 3 hours), all are very unstable and decay with half-lives of a few minutes or less.Sony VAIO VGN-AR690U Battery

The isotope 135Cs is one of the long-lived fission products of uranium which form in nuclear reactors.However, itsfission product yield is reduced in most reactors because its predecessor, 135Xe, is an extremely potent neutron poison and transmutes frequently to stable 136Xe before it can decay to 135Cs.Sony VAIO VGN-AR71ZU Battery

Because of its beta decay (to 137mBa), 137Cs is a strong emitter of gamma radiation. Its half-life makes it the principalmedium-lived fission product along with 90Sr—both are responsible for radioactivity of spent nuclear fuel after several years of cooling up to several hundred years after use.Sony VAIO VGN-AR730E/B Battery

For example 137Cs together with 90Sr currently generate the largest source of radioactivity generated in the area around the Chernobyl disaster. It is not feasible to dispose of 137Cs through neutron capture (due to the low capture rate) and as a result it must be allowed to decay.Sony VAIO VGN-AR73DB Battery

Almost all caesium produced from nuclear fission comes from beta decay of originally more neutron-rich fission products, passing through various isotopes of iodineand of xenon. Because iodine and xenon are volatile and can diffuse through nuclear fuel or air, radioactive caesium is often created far from the original site of fission.Sony VAIO VGN-AR74DB Battery

With the commencement of nuclear weapons testing around 1945, 137Cs was released into the atmosphere and then returned to the surface of the earth as a component of radioactive fallout.

Occurrence

Caesium is a relatively rare element as it is estimated to average approximately 3 parts per million in the Earth's crust.Sony VAIO VGN-AR75UDB Battery

This makes it the 45th most abundant of all elements and the 36th of all the metals. Nevertheless, it is more abundant than such elements as antimony, cadmium, tin and tungsten, and two orders of magnitude more abundant than mercury or silver, but 30 times less abundant than rubidium—with which it is so closely chemically associated.Sony VAIO VGN-AR790U/B Battery

Due to its large ionic radius, caesium is one of the "incompatible elements." During magma crystallization, caesium is concentrated in the liquid phase and crystallizes last. Therefore the largest deposits of caesium are zone pegmatite ore bodies formed by this enrichment process. Sony VAIO VGN-AR820E Battery

Because caesium does not substitute for potassium as readily as does rubidium, the alkali evaporite minerals sylvite (KCl) and carnallite (KMgCl3·6H2O) may contain only 0.002% caesium. Consequently, Cs is found in few minerals. Sony VAIO VGN-AR830E Battery

Percent amounts of caesium may be found in beryl (Be3Al2(SiO3)6) and avogadrite ((K,Cs)BF4), up to 15 wt% Cs2O in the closely related mineral pezzottaite (Cs(Be2Li)Al2Si6O18), up to 8.4 wt% Cs2O in the rare mineral londonite ((Cs,K)Al4Be4(B,Be)12O28), and less in the more widespreadrhodizite.Sony VAIO VGN-AR83S Battery

The only economically important source mineral for caesium is pollucite Cs(AlSi2O6), which is found in a few places around the world in zoned pegmatites, and is associated with the more commercially important lithium minerals lepidolite and petalite. Within the pegmatites, the large grain size and the strong separation of the minerals create high-grade ore for mining.Sony VAIO VGN-AR83US Battery

One of the world's most significant and richest sources of the metal is the Tanco mine at Bernic Lake in Manitoba, Canada. The deposits there are estimated to contain 350,000 metric tons of pollucite ore, which represents more than two-thirds of the world's reserve base.Sony VAIO VGN-AR84S Battery

Although the stoichiometric content of caesium in pollucite is 42.6%, pure pollucite samples from this deposit contain only about 34% caesium, while the average content is 24 wt%. Commercial pollucite contains over 19% caesium. The Bikita pegmatite deposit in Zimbabwe is mined for its petalite but it also contains a significant amount of pollucite. Sony VAIO VGN-AR84US Battery

Notable amounts of pollucite are also mined in the Karibib Desert, Namibia.At the present rate of world mine production of 5 to 10 metric tons per year, reserves will last for thousands of years.

Production

The mining of pollucite ore is a selective process and is conducted on a small scale in comparison with most metal mining operations.Sony VAIO VGN-AR85S Battery

The ore is crushed, hand-sorted, but not usually concentrated, and then ground. Caesium is then extracted from pollucite mainly by three methods: acid digestion, alkaline decomposition, and direct reduction.

In the acid digestion, the silicate pollucite rock is dissolved with strong acids such as hydrochloric (HCl), sulfuric (H2SO4), hydrobromic (HBr), or hydrofluoric(HF). Sony VAIO VGN-AR85US Battery

With hydrochloric acid, a mixture of soluble chlorides is produced, and the insoluble chloride double salts of caesium are precipitated as caesium antimony chloride (Cs4SbCl7), caesium iodine chloride (Cs2ICl), or caesium hexachlorocerate (Cs2(CeCl6)).Sony VAIO VGN-AR870EA Battery

After separation, the pure precipitated double salt is decomposed, and pure CsCl is obtained after evaporating the water. The method using sulfuric acid yields the insoluble double salt directly as caesium alum (CsAl(SO4)2·12H2O). The aluminium sulfate in it is converted to the insoluble aluminium oxide by roasting the alum with carbon, and the resulting product is leached with water to yield a Cs2SO4 solution. Sony VAIO VGN-AR890U Battery

The roasting of pollucite with calcium carbonate and calcium chloride yields insoluble calcium silicates and soluble caesium chloride. Leaching with water or diluteammonia (NH4OH) yields then a dilute chloride (CsCl) solution. This solution can be evaporated to produce caesium chloride or transformed into caesium alum or caesium carbonate.Sony VAIO VGN-AR93S Battery

Albeit not commercially feasible, direct reduction of the ore with potassium, sodium or calcium in vacuum can produce caesium metal directly.

Most of the mined caesium (as salts) is directly converted into caesium formate (HCOO?Cs+) for applications such as oil drilling.Sony VAIO VGN-AR93US Battery

To supply the developing market,Cabot Corporation built a production plant in 1997 at the Tanco Mine near Bernic Lake in Manitoba, Canada, with a capacity of 12,000 barrels (1,900 m3) per year of caesium formate solution. The primary smaller-scale commercial compounds of caesium are caesium chloride and its nitrate.Sony VAIO VGN-AR94S Battery

Alternatively, caesium metal may be obtained from the purified compounds derived from the ore. Caesium chloride, and the other caesium halides as well, can be reduced at 700 to 800 °C (1,292 to 1,472 °F) with calcium or barium, followed by distillation of the caesium metal. In the same way, the aluminate, carbonate, or hydroxide may be reduced by magnesium.Sony VAIO VGN-AR94US Battery

The metal can also be isolated by electrolysis of fused caesium cyanide (CsCN). Exceptionally pure and gas-free caesium can be made by the thermal decomposition at 390 °C (734 °F) of caesium azide CsN3, which is produced from aqueous caesium sulfate and barium azide.Sony VAIO VGN-AR95S Battery

In vacuum applications, caesium dichromate can be reacted with zirconium forming pure caesium metal without other gaseous products.

Cs2Cr2O7 + 2 Zr ? 2 Cs + 2 ZrO2+ Cr2O3

The price of 99.8% pure caesium (metal basis) in 2009 was about US$10 per gram ($280 per ounce), but its compounds are significantly cheaper.Sony VAIO VGN-AR95US Battery

History

In 1860, Robert Bunsen and Gustav Kirchhoff discovered caesium in the mineral water from Dürkheim, Germany. Due to the bright blue lines in its emission spectrum, they chose a name derived from the Latin word caesius, meaning sky-blue.Sony VAIO VGN-AW110J/H Battery

Caesium was the first element to be discovered spectroscopically, only one year after the invention of the spectroscope by Bunsen and Kirchhoff.

To obtain a pure sample of caesium, 44,000 litres (9,700 imp gal; 12,000 US gal) of mineral water had to be evaporated to yield 240 kilograms (530 lb) of concentrated salt solution. Sony VAIO VGN-AW11M/H Battery

The alkaline earth metals were precipitated either as sulfates or oxalates, leaving the alkali metal in the solution. After conversion to the nitrates and extraction with ethanol, a sodium-free mixture was obtained. From this mixture, the lithium was precipitated by ammonium carbonate. Sony VAIO VGN-AW11S/B Battery

Potassium, rubidium and caesium form insoluble salts with chloroplatinic acid, but these salts show a slight difference in solubility in hot water. Therefore, the less-soluble caesium and rubidium hexachloroplatinate ((Cs,Rb)2PtCl6) could be obtained by fractional crystallization.Sony VAIO VGN-AW11XU/Q Battery

After reduction of the hexachloroplatinate with hydrogen, caesium and rubidium could be separated by the difference in solubility of their carbonates in alcohol. The process yielded 9.2 grams (0.32 oz) of rubidium chloride and 7.3 grams (0.26 oz) of caesium chloride from the initial 44,000 liters of mineral water.Sony VAIO VGN-AW11Z/B Battery

The two scientists used the caesium chloride thus obtained to estimate the atomic weight of the new element at 123.35 (compared to the currently accepted one of 132.9). They tried to generate elemental caesium by electrolysis of molten caesium chloride, but instead of a metal, they obtained a blue homogenous substance which "neither under the naked eye nor under the microscope" showed the slightest trace of metallic substance;" as a result, they assigned it as a subchloride (Cs2Cl). Sony VAIO VGN-AW120J/H Battery

In reality, the product was probably a colloidal mixture of the metal and caesium chloride.[58] The electrolysis of the aqueous solution of chloride with a mercury anode produced a caesium amalgam which readily decomposed under the aqueous conditions.Sony VAIO VGN-AW150Y/H Battery

The pure metal was eventually isolated by the German chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen. In 1882 he produced caesium metal by electrolyzing caesium cyanide, and thus avoiding the problems with the chloride.Sony VAIO VGN-AW160J/Q Battery

Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical fields. Very few applications existed for caesium until the 1920s when it became used in radio vacuum tubes. It had two functions: as a getter it removed excess oxygen after manufacture, and as a coating on the heated cathode, it increased its electrical conductivity.Sony VAIO VGN-AW170Y/Q Battery

Caesium did not become recognized as a high-performance industrial metal until the 1950s. Applications of non-radioactive caesium included photoelectric cells, photomultiplier tubes, optical components of infrared spectrophotometers, catalysts for several organic reactions, crystals for scintillation counters, and in magnetohydrodynamic power generators.Sony VAIO VGN-AW180Y/Q Battery

Since 1967, the International System of Measurements has based its unit of time, the second, on the properties of caesium. The International System of Units (SI) defines the second as 9,192,631,770 cycles of the radiation, which corresponds to the transition between two hyperfine energy levels of the ground state of the caesium-133 atom.Sony VAIO VGN-AW190JAH Battery

The 13th General Conference on Weights and Measures of 1967 defined a second as: "the duration of 9,192,631,770 cycles of microwave light absorbed or emitted by the hyperfine transition of caesium-133 atoms in their ground state undisturbed by external fields".Sony VAIO VGN-AW190NAB Battery

Petroleum exploration

The largest current end-use of caesium is in caesium formate-based drilling fluids for the extractive oil industry. Aqueous solutions of caesium formate (HCOO–Cs+)—made by reacting caesium hydroxide with formic acid—were developed in the mid-1990s for use as oil well drilling and completion fluids. Sony VAIO VGN-AW190NBB Battery

The function of caesium formate as a drilling fluid is to lubricate drill bits, to bring rock cuttings to the surface, and to maintain pressure on the formation during drilling of the well. As completion fluid, which assists the emplacement of control hardware after drilling but prior to production, the function of caesium formate is to maintain the pressure.Sony VAIO VGN-AW190NCB Battery

The high density of the caesium formate brine (up to 2.3 g·cm?3, or 19.2 pounds per gallon), coupled with the relatively benign nature of most caesium compounds, reduces the requirement for toxic high-density suspended solids in the drilling fluid—a significant technological, engineering and environmental advantage. Sony VAIO VGN-AW190YAB Battery

Unlike the components of many other heavy liquids, caesium formate is relatively environment-friendly. The caesium formate brine can be blended with potassium and sodium formates to decrease the density of the fluids down to that of water (1.0 g·cm?3, or 8.3 pounds per gallon). Sony VAIO VGN-AW190YBB Battery

Furthermore, it is biodegradable and reclaimable, and may be recycled, which is important in view of its high cost (about $4,000 per barrel in 2001). Alkali formates are safe to handle and do not damage the producing formation or downhole metals as their corrosive alternative, high-density brines (such as zinc bromide ZnBr2 solutions),sometimes do; they also require less cleanup and disposal costs. Sony VAIO VGN-AW190YCB Battery

Atomic clocks

Caesium-based atomic clocks observe electromagnetic transitions in the hyperfine structure of caesium-133 atoms and use it as a reference point. The first accurate caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.Sony VAIO VGN-AW190YDB Battery

Since then, they have been improved repeatedly over the past half-century, and form the basis for standards-compliant time and frequency measurements. These clocks measure frequency with an error of 2 to 3 parts in 1014, which would correspond to a time measurement accuracy of 2 nanoseconds per day, or one second in 1.4 million years. Sony VAIO VGN-AW220J/B Battery

The latest versions are accurate to better than 1 part in 1015, which means they would be off by about 2 seconds since the extinction of the dinosaurs 65 million years ago, and has been regarded as "the most accurate realization of a unit that mankind has yet achieved." Sony VAIO VGN-AW230J/H Battery

Caesium clocks are also used in networks that oversee the timing of cell phone transmissions and the information flow on the Internet.

Electric power and electronics

Caesium vapor thermionic generators are low-power devices that convert heat energy to electrical energy. Sony VAIO VGN-AW235J/B Battery

In the two-electrodevacuum tube converter, it neutralizes the space charge that builds up near the cathode, and in doing so, it enhances the current flow.

Caesium is also important for its photoemissive properties by which light energy is converted to electron flow. Sony VAIO VGN-AW290JFQ Battery

It is used inphotoelectric cells because caesium-based cathodes such as the intermetallic compound K2CsSb have low threshold voltage for emission of electrons. The range of photoemissive devices using caesium include optical character recognition devices,photomultiplier tubes, and video camera tubes.Sony VAIO VGN-AW41JF Battery

Nevertheless, germanium, rubidium, selenium, silicon, tellurium, and several other elements can substitute caesium in photosensitive materials. Sony VAIO VGN-AW41JF/H Battery

Caesium iodide (CsI), bromide (CsBr) and caesium fluoride (CsF) crystals are employed for scintillators in scintillation counterswidely used in mineral exploration and particle physics research as they are well suited for the detection of gamma and x-rayradiation.Sony VAIO VGN-AW41MF Battery

Caesium, being a heavy element, provides good stopping power contributing to better detectivity. Caesium compounds may also provide a faster response (CsF) and be less hygroscopic (CsI).

Caesium vapor is used in many common magnetometers. The element is also used as an internal standard in spectrophotometry.Sony VAIO VGN-AW41MF/H Battery

Like other alkali metals, caesium has a great affinity for oxygen and is used as a "getter" in vacuum tubes. Other uses of the metal include high-energy lasers,vapor glow lamps, and vapor rectifiers. Sony VAIO VGN-AW41XH Battery

Centrifugation fluids

Because of their high density, solutions of caesium chloride (CsCl), sulfate (Cs2SO4), and trifluoroacetate (Cs(O2CCF3)) are commonly used in molecular biology for density gradient ultracentrifugation. Sony VAIO VGN-AW41XH/Q Battery

This technology is primarily applied to the isolation of viral particles, sub-cellular organelles and fractions, andnucleic acids from biological samples.

Chemical and medical use

Relatively few chemical applications exist for caesium.Sony VAIO VGN-AW41ZF Battery

Doping with caesium compounds is used to enhance the effectiveness of several metal-ion catalysts used in the production of chemicals, such as acrylic acid, anthraquinone, ethylene oxide, methanol,phthalic anhydride, styrene, methyl methacrylate monomers, and various olefins.Sony VAIO VGN-AW41ZF/B Battery

It is also used in the catalytic conversion ofsulfur dioxide into sulfur trioxide in the production of sulfuric acid.

Caesium fluoride enjoys niche use in organic chemistry as a base, or as an anhydrous source of fluoride ion. Caesium salts sometimes replace potassium or sodium salts in organic synthesis, such as cyclization, esterification, and polymerization.Sony VAIO VGN-AW50DB/H Battery

Nuclear and isotope applications

Caesium-137 is a very common radioisotope used as a gamma-emitter in industrial applications. Its advantages include a half-life of roughly 30 years, its availability from the nuclear fuel cycle, and having 137Ba as stable end product. Sony VAIO VGN-AW51JGB Battery

The high water solubility is a disadvantage which makes it incompatible with irradiation of food and medical supplies. It has been used in agriculture, cancer treatment, and the sterilization of food, sewage sludge, and surgical equipment. Radioactive isotopes of caesium in radiation devices were used in the medical field to treat certain types of cancer,Sony VAIO VGN-AW52JGB Battery

but emergence of better alternatives and the use of water-soluble caesium chloride in the sources, which could create wide-ranging contamination, gradually put some of these caesium sources out of use. Caesium-137 has been employed in a variety of industrial measurement gauges, including moisture, density, leveling, and thickness gauges.Sony VAIO VGN-AW53FB Battery

It has also been used in well logging devices for measuring the electron density of the rock formations, which is analogous to the bulk density of the formations.

Isotope 137 has also been used in hydrologic studies analogous to those using tritium. It is a daughter product of nuclear fission reactions. Sony VAIO VGN-AW70B/Q Battery

With the commencement of nuclear testing around 1945, and continuing through the mid-1980s, caesium-137 was released into the atmosphere where it is absorbed readily into solution. Known year-to-year variation within that period allows correlation with soil and sediment layers. Sony VAIO VGN-AW71JB Battery

Caesium-134, and to a lesser extent caesium-135, have also been used in hydrology as a measure of caesium output by the nuclear power industry. While they are less prevalent than either caesium-133 or caesium-137, these isotopes have the advantage of being produced solely from anthropogenic sources. Sony VAIO VGN-AW72JB Battery

Other uses

Caesium and mercury were used as a propellant in early ion engines designed for spacecraft propulsion on very long interplanetary or extraplanetary missions. The ionization method was to strip the outer electron from the propellant upon contact with a tungsten electrode that had voltage applied.Sony VAIO VGN-AW73FB Battery

Concerns about the corrosive action of caesium on spacecraft components have pushed development in the direction of use of inert gas propellants such as xenon; this is easier to handle in ground-based tests and has less potential to interfere with the spacecraft.Sony VAIO VGN-AW80NS Battery

Eventually, xenon was used in the experimental spacecraft Deep Space 1 launched in 1998. Nevertheless, field emission electric propulsion thrusters which use a simple system of accelerating liquid metal ions such as of caesium to create thrust have been built.Sony VAIO VGN-AW80S Battery

Caesium nitrate is used as an oxidizer and pyrotechnic colorant to burn silicon in infrared flares such as the LUU-19 flare,because it emits much of its light in the near infrared spectrum.Caesium has been used to reduce theradar signature of exhaust plumes in the SR-71 Blackbird military aircraft.Sony VAIO VGN-AW80US Battery

Caesium, along with rubidium, has been added as a carbonate to glass because it reduces electrical conductivity and improves stability and durability offiber optics and night vision devices. Caesium fluoride or caesium aluminium fluoride are used in fluxes formulated for the brazing of aluminium alloys that contain magnesium.Sony VAIO VGN-AW81DS Battery

Prognostications

Magnetohydrodynamic (MHD) power-generating systems were researched but failed to gain widespread acceptance.Caesium metal has also been considered as the working fluid in high-temperature Rankine cycle turboelectric generators.Sony VAIO VGN-AW81JS Battery

Caesium salts have been evaluated as antishock reagents to be used following the administration of arsenical drugs. Because of their effect on heart rhythms, however, they are less likely to be used than potassium or rubidium salts. They have also been used to treat epilepsy.Sony VAIO VGN-AW81YS Battery

Health and safety hazards

Caesium compounds are rarely encountered by most people, but most caesium compounds are mildly toxic because of chemical similarity of caesium to potassium. Exposure to large amounts of caesium compounds can causehyperirritability and spasms, Sony VAIO VGN-AW82DS Battery

but as such amounts would not ordinarily be encountered in natural sources, caesium is not a major chemical environmental pollutant. The median lethal dose (LD50) value for caesium chloride in mice is 2.3 g per kilogram, which is comparable to the LD50values of potassium chloride and sodium chloride.Sony VAIO VGN-AW82JS Battery

Caesium metal is one of the most reactive elements and is highly explosive when it comes in contact with water. The hydrogen gas produced by the reaction is heated by the thermal energy released at the same time, causing ignition and a violent explosion. Sony VAIO VGN-AW82YS Battery

This can occur with other alkali metals, but caesium is so potent that this explosive reaction can even be triggered by cold water. The metal is highly pyrophoric, and ignites spontaneously in air to form caesium hydroxide and various oxides. Caesium hydroxide is a very strong base, and can rapidly corrode glass.Sony VAIO VGN-AW83FS Battery

The isotopes 134 and 137 (present in the biosphere in small amounts from radiation leaks) represent a radioactivity burden which varies depending on location. Radiocaesium does not accumulate in the body as effectively as many other fission products (such as radioiodine and radiostrontium).Sony VAIO VGN-AW83GS Battery

As with other alkali metals, radiocaesium washes out of the body relatively quickly in sweat and urine. However, radiocaesium follows potassium and tends to accumulate in plant tissues, including fruits and vegetables. It is also well-documented that mushrooms from contaminated forests accumulate radiocaesium (caesium-137) in their fungalsporocarps.Sony VAIO VGN-AW83HS Battery

Accumulation of caesium-137 in lakes has been a high concern after the Chernobyl disaster. Experiments with dogs showed that a single dose of 3.8 millicuries (140 MBq, 4.1 ?g of caesium-137) per kilogram is lethal within three weeks; smaller amounts may cause infertility and cancer.Sony VAIO VGN-AW90NS Battery

TheInternational Atomic Energy Agency and other sources have warned that radioactive materials, such as caesium-137, could be used in radiological dispersion devices, or "dirty bombs".Sony VAIO VGN-AW90S Battery,Sony VAIO VGN-AW90US Battery,Sony VAIO VGN-AW91CDS Battery,Sony VAIO VGN-AW91CJS Battery,Sony VAIO VGN-AW91CYS Battery,Sony VAIO VGN-AW91DS Battery