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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

tm" title="Sony VGP-BPS7 laptop 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

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