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Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature HP Pavilion DV4-1199EA Battery

. Andrés Manuel del Río discovered vanadium in 1801 by analyzing a new lead-bearing mineral he called "brown lead," and named the new element erythronium (Greek for "red") since, upon heating, most of its salts turned from their initial color to red. Four years later, however, he was convinced by other scientists that erythronium was identical to chromium.HP Pavilion DV4-1199EE Battery

The element was rediscovered in 1831 by Nils Gabriel Sefström, who named it vanadium after the Germanic goddess of beauty and fertility, Vanadís (Freyja). Both names were attributed to the wide range of colors found in vanadium compounds. Del Rio's lead mineral was later renamed vanadinite for its vanadium content.HP Pavilion DV4-1199EF Battery

The element occurs naturally in about 65 different minerals and in fossil fuel deposits. It is produced in China and Russia from steel smelter slag; other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. It is mainly used to produce specialty steel alloys such as high speed tool steels.HP Pavilion DV4-1199EO Battery

The most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid.

Large amounts of vanadium ions are found in a few organisms, possibly as a toxin. The oxide and some other salts of vanadium have moderate toxicity.HP Pavilion DV4-1199EP Battery

Particularly in the ocean, vanadium is used by some life forms as an active center of enzymes, such as the vanadium bromoperoxidase of some ocean algae. Vanadium is probably a micronutrient in mammals, including humans, but its precise role in this regard is unknown.HP Pavilion DV4-1199ER Battery

Vanadium was originally discovered by Andrés Manuel del Río, a Spanish-born Mexican mineralogist, in 1801. Del Río extracted the element from a sample of Mexican "brown lead" ore, later named vanadinite. He found that its salts exhibit a wide variety of colors, and as a result he named the element panchromium (Greek: ????????? "all colors").HP Pavilion DV4-1199ES Battery

Later, Del Río renamed the element erythronium (Greek: ??????? "red") as most of its salts turned red upon heating. In 1805, the French chemistHippolyte Victor Collet-Descotils, backed by del Río's friend Baron Alexander von Humboldt, incorrectly declared that del Río's new element was only an impure sample of chromium.HP Pavilion DV4-1199ET Battery

Del Río accepted the Collet-Descotils' statement and retracted his claim.

In 1831, the Swedish chemist Nils Gabriel Sefström rediscovered the element in a new oxide he found while working with iron ores. Later that same year, Friedrich Wöhler confirmed del Río's earlier work.HP Pavilion DV4-1200 CTO Battery

Sefström chose a name beginning with V, which had not been assigned to any element yet. He called the element vanadium after Old Norse Vanadís (another name for theNorse Vanr goddess Freyja, whose facets include connections to beauty and fertility), because of the many beautifully coloredchemical compounds it produces.HP Pavilion DV4-1200 Battery

In 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed "rionium" after del Río, but this suggestion was not followed.

The isolation of vanadium metal proved difficult. In 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had in fact produced the nitride, vanadium nitride (VN).HP Pavilion DV4-1201AU Battery

Roscoe eventually produced the metal in 1867 by reduction of vanadium(II) chloride, VCl2, with hydrogen. In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium. The first large scale industrial use of vanadium in steels was found in the chassis of the Ford Model T, inspired by French race cars.HP Pavilion DV4-1201TU Battery

Vanadium steel allowed for reduced weight while simultaneously increasingtensile strength.

Characteristics

Vanadium is a hard, ductile, silver-gray metal. Some sources describe vanadium as "soft", perhaps because it is ductile, malleable and not brittle.HP Pavilion DV4-1201TX Battery

Vanadium is harder than most metals and steels (see Hardnesses of the elements (data page)and iron). It has good resistance to corrosion and it is stable against alkalis, sulfuric and hydrochloric acids.[10] It isoxidized in air at about 933 K (660 °C, 1220 °F), although an oxide layer forms even at room temperature.HP Pavilion DV4-1202AU Battery

Isotopes

Naturally occurring vanadium is composed of one stable isotope 51V and one radioactive isotope 50V. The latter has a half-lifeof 1.5×1017 years and a natural abundance 0.25%. 51V has a nuclear spin of 7/2 which is useful for NMR spectroscopy.HP Pavilion DV4-1202TU Battery

A number of 24 artificial radioisotopes have been characterized, ranging in mass number from 40 to 65. The most stable of these isotopes are 49V with a half-life of 330 days, and 48V with a half-life of 16.0 days. All of the remaining radioactiveisotopes have half-lives shorter than an hour, most of which are below 10 seconds.HP Pavilion DV4-1202TX Battery

At least 4 isotopes have metastable excited states. Electron capture is the main decay mode for isotopes lighter than the 51V. For the heavier ones, the most common mode is beta decay. The electron capture reactions lead to the formation of element 22 (titanium) isotopes, while for beta decay, it leads to element 24 (chromium) isotopes.HP Pavilion DV4-1203AU Battery

Chemistry and compounds

The chemistry of vanadium is noteworthy for the accessibility of the four adjacent oxidation states 2-4. In aqueous solution the colours are lilac V2+(aq), green V3+(aq), blue VO2+(aq) and, at high pH, yellow VO42-. Vanadium(II) compounds are reducing agents, and vanadium(V) compounds are oxidizing agents.HP Pavilion DV4-1203TU Battery

Vanadium(IV) compounds often exist as vanadyl derivatives which contain the VO2+ center.

Ammonium vanadate(V) (NH4VO3) can be successively reduced with elemental zinc to obtain the different colors of vanadium in these four oxidation states.HP Pavilion DV4-1203TX Battery

Lower oxidation states occur in compounds such as V(CO)6, [V(CO)6]? and substituted derivatives.

The vanadium redox battery utilizes these oxidation states; conversion of these oxidation states is illustrated by the reduction of a strongly acidic solution of a vanadium(V) compound with zinc dust.HP Pavilion DV4-1204AU Battery

The initial yellow color characteristic of the vanadate ion, VO3?

4, is replaced by the blue color of [VO(H2O)5]2+, followed by the green color of [V(H2O)6]3+ and then violet, due to [V(H2O)6]2+.HP Pavilion DV4-1204TU Battery

The most commercially important compound is vanadium pentoxide, which is used as a catalyst for the production of sulfuric acid.[10] This compound oxidizes sulfur dioxide (SO2) to the trioxide (SO3). In thisredox reaction, sulfur is oxidized from +4 to +6, and vanadium is reduced from +5 to +3:HP Pavilion DV4-1204TX Battery

V2O5 + 2 SO2 ? V2O3 + 2 SO3

The catalyst is regenerated by oxidation with air:

V2O3 + O2 ? V2O5

Oxy and oxo compounds

The oxyanion chemistry of vanadium(V) is complex. The vanadate ion, VO3?4, is present in dilute solutions at high pH. On acidification, HVO2?4 and H2VO?4 are formed, analogous to HPO2?4 and H2PO?4.HP Pavilion DV4-1205AU Battery

The acid dissociation constants for the vanadium and phosphorus series are remarkably similar. In more concentrated solutions many polyvanadates are formed. Chains, rings and clusters involving tetrahedral vanadium, analogous to the polyphosphates, are known.HP Pavilion DV4-1205TU Battery

In addition, clusters such as the decavanadates V10O4?28 and HV10O3?28, which predominate at pH 4–6, are formed in which there is a distorted octahedron of oxygen atoms around each vanadium atom.[10]

The correspondence between vanadate and phosphate chemistry can be attributed to the similarity in size and charge of phosphorus(V) and vanadium(V).HP Pavilion DV4-1205TX Battery

Orthovanadate VO3?4 is used in protein crystallography[13] to study the biochemistry of phosphate.[14]

Vanadium also forms various peroxo- complexes when treated with hydrogen peroxide. For instance, the yellow oxovanadium(V) ion VO+
2in acidic hydrogen peroxide solution forms the brick red peroxovanadium(V) ion, VO(O2)2+.HP Pavilion DV4-1206TU Battery

Halide compounds

All four halides are known for oxidation states +2 and +3, but the iodide is not known for V(IV) and VF5 is the only halide known for oxidation state 5. VCl4 may be used as a catalyst for polymerization of dienes.HP Pavilion DV4-1206TX Battery

Coordination compounds

Vanadium's early position in the transition metal series lead to three rather unusual features of the coordination chemistry of vanadium. Firstly, metallic vanadium has the electronic configuration [Ar]3d34s2, so compounds of vanadium are relatively electron-poor.HP Pavilion DV4-1207TU Battery

Consequently, most binary compounds are Lewis acids (electron pair acceptors); examples are all the halides forming octahedral adducts with the formula VXnL6?n (X = halide; L = other ligand). Secondly, the vanadium ion is rather large and can achieve coordination numbers higher than 6, as is the case in [V(CN)7]4?.HP Pavilion DV4-1207TX Battery

Thirdly, the vanadyl ion, VO2+, is featured in many complexes of vanadium(IV) such as vanadyl acetylacetonate (V(=O)(acac)2). In this complex, the vanadium is 5-coordinate, square pyramidal, meaning that a sixth ligand, such as pyridine, may be attached, though the association constant of this process is small.HP Pavilion DV4-1208TU Battery

Many 5-coordinate vanadyl complexes have a trigonal bypyramidal geometry, such as VOCl2(NMe3)2.

Organometallic compounds

Organometallic chemistry of vanadium is well developed, but organometallic compounds are of minor commercial significance.HP Pavilion DV4-1208TX Battery

Vanadocene dichloride is a versatile starting reagent and even finds minor applications in organic chemistry.[17] Vanadium carbonyl, V(CO)6, is a rare example of ametal carbonyl containing an unpaired electron, but which exists without dimerization.HP Pavilion DV4-1209TU Battery

The addition of an electron yields V(CO)?6 (isoelectronic with Cr(CO)6), which may be further reduced with sodium in liquid ammonia to yield V(CO)3?6 (isoelectronic with Fe(CO)5).

Occurrence

Metallic vanadium is not found in nature, but is known to exist in about 65 different minerals.HP Pavilion DV4-1209TX Battery

Economically significant examples include patronite (VS4), vanadinite (Pb5(VO4)3Cl), and carnotite (K2(UO2)2(VO4)2·3H2O). Much of the world's vanadium production is sourced from vanadium-bearing magnetite found in ultramafic gabbro bodies.HP Pavilion DV4-1210EA Battery

Vanadium is mined mostly in South Africa, north-western China, and eastern Russia. In 2010 these three countries mined more than 98% of the 56,000 tonnes of produced vanadium.

Vanadium is also present in bauxite and in fossil fuel deposits such as crude oil, coal, oil shale and tar sands.HP Pavilion DV4-1210EF Battery

In crude oil, concentrations up to 1200 ppm have been reported. When such oil products are burned, the traces of vanadium may initiate corrosionin motors and boilers. An estimated 110,000 tonnes of vanadium per year are released into the atmosphere by burning fossil fuels.HP Pavilion DV4-1210EO Battery

Vanadium has also been detected spectroscopically in light from the Sun and some other stars.

Production

Most vanadium is used as an alloy called ferrovanadium as an additive to improve steels.Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace.HP Pavilion DV4-1210ER Battery

Vanadium-bearing magnetite iron ore is the main source for the production of vanadium. The vanadium ends up in pig iron produced from vanadium bearing magnetite. During steel production, oxygen is blown into the pig iron, oxidizing the carbon and most of the other impurities, forming slag.HP Pavilion DV4-1210TU Battery

Depending on the used ore, the slag contains up to 25% of vanadium.

Vanadium metal is obtained via a multistep process that begins with the roasting of crushed ore with NaCl or Na2CO3 at about 850 °C to give sodium metavanadate (NaVO3). An aqueous extract of this solid is acidified to give "red cake", a polyvanadate salt, which is reduced with calcium metal.HP Pavilion DV4-1210TX Battery

As an alternative for small scale production, vanadium pentoxide is reduced with hydrogen or magnesium. Many other methods are also in use, in all of which vanadium is produced as a byproduct of other processes. Purification of vanadium is possible by the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925.HP Pavilion DV4-1211EA Battery

It involves the formation of the metal iodide, in this example vanadium(III) iodide, and the subsequent decomposition to yield pure metal.

2 V + 3 I2 2 VI3

Alloys

Approximately 85% of vanadium produced is used as ferrovanadium or as a steel additive.HP Pavilion DV4-1211TU Battery

The considerable increase of strength in steel containing small amounts of vanadium was discovered in the beginning of the 20th century. Vanadium forms stable nitrides and carbides, resulting in a significant increase in the strength of the steel.HP Pavilion DV4-1211TX Battery

From that time on vanadium steel was used for applications in axles, bicycle frames,crankshafts, gears, and other critical components. There are two groups of vanadium containing steel alloy groups. Vanadium high-carbon steel alloys contain 0.15% to 0.25% vanadium and high speed tool steels (HSS) have a vanadium content of 1% to 5%.HP Pavilion DV4-1212LA Battery

For high speed tool steels, a hardness above HRC 60 can be achieved. HSS steel is used in surgical instruments and tools.[28]

Vanadium stabilizes the beta form of titanium and increases the strength and temperature stability of titanium. Mixed with aluminium in titanium alloys it is used in jet engines and high-speed airframes.HP Pavilion DV4-1212TU Battery

One of the common alloys is Titanium 6AL-4V, a titanium alloy with 6% aluminium and 4% vanadium.

Other uses

Vanadium is compatible with iron and titanium, therefore vanadium foil is used in cladding titanium to steel.HP Pavilion DV4-1212TX Battery

The moderate thermal neutron-capture cross-section and the short half-life of the isotopes produced by neutron capture makes vanadium a suitable material for the inner structure of a fusion reactor. Several vanadium alloys show superconducting behavior. The first A15 phase superconductor was a vanadium compound, V3Si, which was discovered in 1952.HP Pavilion DV4-1213LA Battery

Vanadium-gallium tape is used in superconducting magnets (17.5 teslas or 175,000 gauss). The structure of the superconducting A15 phase of V3Ga is similar to that of the more common Nb3Sn and Nb3Ti.

The most common oxide of vanadium, vanadium pentoxide V2O5, is used as a catalyst in manufacturing sulfuric acid by the contact process and as an oxidizer in maleic anhydride production.HP Pavilion DV4-1213TU Battery

Vanadium pentoxide is also used in making ceramics. Another oxide of vanadium, vanadium dioxide VO2, is used in the production of glass coatings, which blocks infrared radiation (and not visible light) at a specific temperature. Vanadium oxide can be used to induce color centers in corundum to create simulated alexandrite jewelry, although alexandrite in nature is a chrysoberyl.HP Pavilion DV4-1213TX Battery

The possibility to use vanadium redox couples in both half-cells, thereby eliminating the problem of cross contamination by diffusion of ions across the membrane is the advantage of vanadium redox rechargeable batteries. Vanadate can be used for protecting steel against rust and corrosion by electrochemical conversion coating.HP Pavilion DV4-1214LA Battery

Lithium vanadium oxide has been proposed for use as a high energy density anode for lithium ion batteries, at 745 Wh/L when paired with a lithium cobalt oxide cathode. It has been proposed by some researchers that a small amount, 40 to 270 ppm, of vanadium in Wootz steel andDamascus steel, significantly improves the strength of the material, although it is unclear what the source of the vanadium was.HP Pavilion DV4-1214TU Battery

Biological role

Vanadium plays a very limited role in biology, and is more important in ocean environments than on land.

Bromoperoxidases in algae

Organobromine compounds in a number of species of marine algae are generated by the action of a vanadium dependentbromoperoxidase.HP Pavilion DV4-1214TX Battery

This is a haloperoxidase in algae which requires bromide and is an absolutely vanadium-dependent enzyme. Most organobromine compounds in the sea ultimately arise via the action of this vanadium bromoperoxidase.

Vanadium accumulation in tunicates and ascidians

German chemist Martin Henze discovered vanadium in the blood cells (or coelomic cells) of Ascidiacea (sea squirts) in 1911.HP Pavilion DV4-1215EF Battery

It is essential to ascidians and tunicates, where it is stored in the highly acidified vacuoles of certain blood cell types, designated vanadocytes. Vanabins (vanadium binding proteins) have been identified in the cytoplasm of such cells. The concentration of vanadium in their blood is up to 10 million times higher than the concentration of vanadium in the seawater around them.HP Pavilion DV4-1215TU Battery

Vanadium has been reported in high concentrations in holothurian (sea cucumber) blood, however other researchers have been unable to reproduce these results. There is no evidence that hemovanadin carries oxygen, in contrast to hemoglobin and hemocyanin, which may also be present in these organisms.HP Pavilion DV4-1215TX Battery

Nitrogen fixation

A vanadium nitrogenase is used by some nitrogen-fixing micro-organisms, such as Azotobacter. In this role vanadium replaces more common molybdenum or iron, and gives the nitrogenase slightly different properties.HP Pavilion DV4-1216TU Battery

Fungi

Several species of macrofungi, namely Amanita muscaria and related species, accumulate vanadium (up to 500 mg/kg in dry weight). Vanadium is present in the coordination complex, amavadin, in fungal fruit-bodies. However, the biological importance of the accumulation process is unknown.HP Pavilion DV4-1216TX Battery

Toxin functions or peroxidase enzyme functions have been suggested.

Mammals and birds

Rats and chickens are also known to require vanadium in very small amounts and deficiencies result in reduced growth and impairedreproduction.HP Pavilion DV4-1217LA Battery

Vanadium is a relatively controversial dietary supplement, primarily for increasing insulin sensitivity[55] andbody-building. Whether it works for the latter purpose has not been proven, and there is some evidence that athletes who take it are merely experiencing a placebo effect.HP Pavilion DV4-1217TX Battery

Vanadyl sulfate may improve glucose control in people with type 2 diabetes. In addition, decavanadate and oxovanadates are species that potentially have many biological activities and that have been successfully used as tools in the comprehension of several biochemical processes.HP Pavilion DV4-1218TX Battery

Safety

All vanadium compounds should be considered to be toxic. Tetravalent VOSO4 has been reported to be over 5 times more toxic than trivalent V2O3.HP Pavilion DV4-1219TX Battery

The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.05 mg/m3 for vanadium pentoxide dust and 0.1 mg/m3 for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week.HP Pavilion DV4-1220BR Battery

TheNational Institute for Occupational Safety and Health (NIOSH) has recommended that 35 mg/m3 of vanadium be considered immediately dangerous to life and health. This is the exposure level of a chemical that is likely to cause permanent health problems or death. HP Pavilion DV4-1220TX Battery

Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation exposures to vanadium and vanadium compounds result primarily in adverse effects on the respiratory system. Quantitative data are, however, insufficient to derive a subchronic or chronic inhalation reference dose.HP Pavilion DV4-1220US Battery

Other effects have been reported after oral or inhalation exposures on blood parameters, on liver,[70] on neurological development in rats,[71] and other organs.[72]

There is little evidence that vanadium or vanadium compounds are reproductive toxins or teratogens.HP Pavilion DV4-1221TX Battery

Vanadium pentoxide was reported to be carcinogenic in male rats and male and female mice by inhalation in an NTP study,[66]although the interpretation of the results has recently been disputed.[73] Vanadium has not been classified as to carcinogenicity by the United States Environmental Protection Agency.HP Pavilion DV4-1222LA Battery

Vanadium traces in diesel fuels present a corrosion hazard; it is the main fuel component influencing high temperature corrosion. During combustion, it oxidizes and reacts with sodium and sulfur, yielding vanadate compounds with melting points down to 530 °C, which attack the passivation layer on steel, rendering it susceptible to corrosion.HP Pavilion DV4-1222NR Battery

The solid vanadium compounds also cause abrasion of engine components.

Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point.HP Pavilion DV4-1222TX Battery

It is also odorless, tasteless, and malleable. The name of the element is derived from the Greek word "chr?ma" (?????), meaningcolour, because many of its compounds are intensely coloured. Chromium oxide was used by the Chinese in the Qin dynastyover 2,000 years ago to coat weapons such as bronze crossbow bolts and steel swords found at the Terracotta Army.HP Pavilion DV4-1223LA Battery

It later came to the attention of the west when it was discovered by Louis Nicolas Vauquelin in the mineral crocoite (lead(II) chromate) in 1797. Crocoite was used as a pigment, and after the discovery that the mineral chromite also contains chromium, this latter mineral was used to produce pigments as well.HP Pavilion DV4-1223TX Battery

Chromium was regarded with great interest because of its high corrosion resistance and hardness. A major development was the discovery that steel could be made highly resistant to corrosion and discoloration by adding chromium to form stainless steel.HP Pavilion DV4-1224LA Battery

This application, along with chrome plating (electroplating with chromium) are currently the highest-volume uses of the metal. Chromium and ferrochromium are produced from the single commercially viable ore, chromite, by silicothermic oraluminothermic reaction or by roasting and leaching processes.HP Pavilion DV4-1224TX Battery

Although trivalent chromium (Cr(III)) is required in trace amounts for sugar and lipid metabolism, few cases have been reported where its complete removal from the diet has caused chromium deficiency. In larger amounts and different forms chromium can be toxic and carcinogenic.HP Pavilion DV4-1225DX Battery

The most prominent example of toxic chromium is hexavalent chromium (Cr(VI)). Abandoned chromium production sites often require environmental cleanup.

Physical

Chromium is remarkable for its magnetic properties: it is the only elemental solid which shows antiferromagnetic ordering at room temperature (and below). Above 38 °C, it transforms into a paramagnetic state.HP Pavilion DV4-1225EE Battery

Passivation

Chromium metal left standing in air is passivated by oxygen, forming a thin protective oxide surface layer. This layer is aspinel structure only a few atoms thick. It is very dense, and prevents the diffusion of oxygen into the underlying material.HP Pavilion DV4-1225LA Battery

This barrier is in contrast to iron or plain carbon steels, where the oxygen migrates into the underlying material and causesrusting. The passivation can be enhanced by short contact with oxidizing acids like nitric acid. Passivated chromium is stable against acids. HP Pavilion DV4-1225TX Battery

The opposite effect can be achieved by treatment with a strong reducing reactant that destroys the protective oxide layer on the metal. Chromium metal treated in this way readily dissolves in weak acids.HP Pavilion DV4-1226TX Battery

Chromium, unlike metals such as iron and nickel, does not suffer from hydrogen embrittlement. However, it does suffer from nitrogen embrittlement, reacting with nitrogen from air and forming brittle nitrides at the high temperatures necessary to work the metal parts.HP Pavilion DV4-1227LA Battery

Occurrence

Chromium is the 21st most abundant element in Earth's crust with an average concentration of 100 ppm. Chromium compounds are found in the environment, due to erosion of chromium-containing rocks and can be distributed by volcanic eruptions.HP Pavilion DV4-1227TX Battery

The concentrations range in soil is between 1 and 3000 mg/kg, in sea water 5 to 800 µg/liter, and in rivers and lakes 26 µg/liter to 5.2 mg/liter.

Chromium is mined as chromite (FeCr2O4) ore.HP Pavilion DV4-1227US Battery

About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa.HP Pavilion DV4-1228CA Battery

Although rare, deposits of native chromium exist. The Udachnaya Pipe in Russia produces samples of the native metal. This mine is a kimberlite pipe, rich in diamonds, and the reducing environment helped produce both elemental chromium and diamond.HP Pavilion DV4-1228LA Battery

The relation between Cr(III) and Cr(VI) strongly depends on pH and oxidative properties of the location, but in most cases, the Cr(III) is the dominating species,[7] although in some areas the ground water can contain up to 39 µg/liter of total chromium of which 30 µg/liter is present as Cr(VI).HP Pavilion DV4-1228TX Battery

Naturally occurring chromium is composed of three stable isotopes; 52Cr, 53Cr and 54Cr with 52Cr being the most abundant (83.789% natural abundance). 19 radioisotopeshave been characterized with the most stable being 50Cr with a half-life of (more than) 1.8×1017 years, and 51Cr with a half-life of 27.7 days.HP Pavilion DV4-1229LA Battery

All of the remainingradioactive isotopes have half-lives that are less than 24 hours and the majority of these have half-lives that are less than 1 minute. This element also has 2 meta states.

53Cr is the radiogenic decay product of 53Mn. Chromium isotopic contents are typically combined with manganese isotopic contents and have found application inisotope geology.HP Pavilion DV4-1229TX Battery

Mn-Cr isotope ratios reinforce the evidence from 26Al and 107Pd for the early history of the solar system. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate an initial 53Mn/55Mn ratio that suggests Mn-Cr isotopic composition must result from in-situ decay of 53Mn in differentiated planetary bodies.HP Pavilion DV4-1230BR Battery

Hence 53Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.

The isotopes of chromium range in atomic mass from 43 u (43Cr) to 67 u (67Cr). The primary decay mode before the most abundant stable isotope, 52Cr, is electron capture and the primary mode after is beta decay.HP Pavilion DV4-1230TX Battery

53Cr has been posited as a proxy for atmospheric oxygen concentration.

Chromium is a member of the transition metals, in group 6. Chromium(0) has an electronic configuration of 4s13d5, owing to the lower energy of the high spin configuration.HP Pavilion DV4-1231TX Battery

Chromium exhibits a wide range of possible oxidation states, where the +3 state is most stable energetically; the +3 and +6 states are most commonly observed in chromium compounds, whereas the +1, +4 and +5 states are rare.

A large number of chromium(III) compounds are known. HP Pavilion DV4-1232TX Battery

Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid. The Cr3+ ion has a similar radius (63 pm) to theAl3+ ion (radius 50 pm), so they can replace each other in some compounds, such as in chrome alum and alum.HP Pavilion DV4-1233TX Battery

When a trace amount of Cr3+ replaces Al3+ in corundum (aluminium oxide, Al2O3), the red-colored ruby is formed.

Chromium(III) ions tend to adopt octahedral molecular geometry, with six ligands. The colors of these solutions is determined by the ligands attached to the Cr centre.HP Pavilion DV4-1234TX Battery

HP Pavilion DV4-1235EE Battery

The commercially available chromium(III) chloride hydrate is the dark green complex [CrCl2(H2O)4]Cl, but two other forms are known: pale green [CrCl(H2O)5]Cl2, and the violet [Cr(H2O)6]Cl3. If water-free green chromium(III) chloride is dissolved in water then the green solution turns violet after some time, due to the substitution of water for chloride in the inner coordination sphere.HP Pavilion DV4-1235EI Battery

This kind of reaction is also observed in chrome alum solutions and other water-soluble chromium(III) salts. The reverse reaction may be induced by heating the solution.

Chromium(III) hydroxide (Cr(OH)3) is amphoteric, dissolving in acidic solutions to form [Cr(H2O)6]3+, and in basic solutions to form[Cr(OH)6]3?.HP Pavilion DV4-1235TX Battery

It is dehydrated by heating to form the green chromium(III) oxide (Cr2O3), which is the stable oxide with a crystal structure identical to that ofcorundum.[4]

Chromium(VI)

Chromium(VI) compounds are powerful oxidants at low or neutral pH. Most important are chromate anion (CrO2?
4) and dichromate (Cr2O72-) anions, which exist in equilibrium:HP Pavilion DV4-1236TX Battery

2 [CrO4]2- + 2 H+ [Cr2O7]2- + 2 H2O

Chromium(VI) halides are known also and include hexafluoride CrF6 and chromyl chloride (CrO2Cl2).[4]

Sodium chromate is produced industrially by the oxidative roasting of chromite ore with calcium or sodium carbonate. The dominant species is therefore, by the law of mass action, determined by the pH of the solution.HP Pavilion DV4-1237TX Battery

The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate. At yet lower pH values, further condensation to more complex oxyanions of chromium is possible.HP Pavilion DV4-1238TX Battery

Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO5) is formed, which can be stabilized as an ether adduct CrO5·OR2.

Chromic acid has the hypothetical formula H2CrO4.HP Pavilion DV4-1239TX Battery

It is a vaguely described chemical, despite many well-defined chromates and dichromates are known. The dark red chromium(VI) oxide CrO3, the acid anhydride of chromic acid, is sold industrially as "chromic acid".[4] It can be produced by mixing sulfuric acid with dichromate, and is a strong oxidizing agent.HP Pavilion DV4-1240TX Battery

In 2010, the Environmental Working Group studied the drinking water in 35 American cities. The study was the first nationwide analysis measuring the presence of the chemical in U.S. water systems. The study found measurable hexavalent chromium in the tap water of 31 of the cities sampled, with Norman, Oklahoma, at the top of list;HP Pavilion DV4-1241TX Battery

25 cities had levels that exceeded California's proposed limit.[20] Note: Concentrations of Cr VI in US municipal drinking water supplies reported by EWG are within likely, natural background levels for the areas tested and not necessarily indicative of industrial pollution (CalEPA Fact Sheet), as asserted by EWG. This factor was not taken into consideration in their report.HP Pavilion DV4-1242TX Battery

Chromium(IV) and chromium(V)

The oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate. The only binary compound is the volatile chromium(V) fluoride (CrF5). This red solid has a melting point of 30 °C and a boiling point of 117 °C.HP Pavilion DV4-1243TX Battery

It can be synthesized by treating chromium metal with fluorine at 400 °C and 200 bar pressure. The peroxochromate(V) is another example of the +5 oxidation state. Potassium peroxochromate (K3[Cr(O2)4]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures.HP Pavilion DV4-1244TX Battery

This red brown compound is stable at room temperature but decomposes spontaneously at 150–170 °C.

Compounds of chromium(IV) (in the +4 oxidation state) are slightly more common than those of chromium(V). The tetrahalides, CrF4, CrCl4, and CrBr4, can be produced by treating the trihalides (CrX3) with the corresponding halogen at elevated temperatures.HP Pavilion DV4-1245BR Battery

Such compounds are susceptible to disproportionation reactions and are not stable in water.

Chromium(I) and chromium(II)

Many chromium(II) compounds are known, including the water-stable chromium(II) chloride, CrCl2, which can be made by reduction of chromium(III) chloride with zinc. HP Pavilion DV4-1245TX Battery

The resulting bright blue solution is only stable at neutral pH.[4] Many chromous carboxylates are also known, most famously, the red chromous acetate (Cr2(O2CCH3)4), which features a quadruple bond. As verified by X-ray diffraction, a Cr-Cr quintuple bond (length 183.51(4) pm) has also been described.HP Pavilion DV4-1246TX Battery

Extremely bulky monodentate ligands stabilize this compound by shielding the quintuple bond from further reactions.

Chromium(0)

Many chromium(0) compounds are known. Most are derivatives of chromium hexacarbonyl or bis(benzene)chromium.HP Pavilion DV4-1247TX Battery

Weapons found in burial pits dating from the late 3rd century BC Qin Dynasty of the Terracotta Army near Xi'an, China have been analyzed by archaeologists. Although buried more than 2,000 years ago, the ancient bronze tips of crossbow bolts and swords found at the site showed no sign of corrosion, because the bronze was coated with chromium.HP Pavilion DV4-1248TX Battery

Chromium later came to the attention of westerners in the 18th century. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Beryozovskoye mines in the Ural Mountains which he named Siberian red lead. Though misidentified as a lead compound withselenium and iron components, the mineral was Crocoite (lead chromate) with a formula of PbCrO4.HP Pavilion DV4-1249TX Battery

In 1770, Peter Simon Pallas visited the same site as Lehmann and found a red lead mineral that had useful properties as a pigment inpaints. The use of Siberian red lead as a paint pigment developed rapidly. A bright yellow pigment made from crocoite also became fashionable.HP Pavilion DV4-1250TX Battery

In 1797, Louis Nicolas Vauquelin received samples of crocoite ore. He produced chromium trioxide (CrO3) by mixing crocoite withhydrochloric acid. In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven.He was also able to detect traces of chromium in precious gemstones, such as ruby or emerald.HP Pavilion DV4-1251TX Battery

During the 1800s, chromium was primarily used as a component of paints and in tanning salts. At first, crocoite from Russia was the main source, but in 1827, a larger chromite deposit was discovered near Baltimore, United States. This made the United states the largest producer of chromium products till 1848 when large deposits of chromite where found near Bursa, Turkey.HP Pavilion DV4-1252TX Battery

Chromium is also known for its luster when polished. It is used as a protective and decorative coating on car parts, plumbing fixtures, furniture parts and many other items, usually applied by electroplating. Chromium was used for electroplating as early as 1848, but this use only became widespread with the development of an improved process in 1924.HP Pavilion DV4-1253TX Battery

Metal alloys now account for 85% of the use of chromium. The remainder is used in the chemical industry and refractory and foundryindustries.

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