This article is about the chemical element. For other uses, see Tungsten (disambiguation). tantalum ← tungsten → rhenium Mo ↑ W ↓ Sg 74W Periodic table Appearance grayish white, lustrous General properties Name, symbol, number tungsten, W, 74 Pronunciation /ˈtʌŋstən/; alternatively, /ˈwʊlfrəm/ WOOL-frəm Element category transition metal Group, period, block 6, 6, d Standard atomic weight 183.84g·mol−1 Electron configuration Xe 4f14 5d4 6s21 Electrons per shell 2, 8, 18, 32, 12, 2 (Image) Physical properties Phase solid Density (near r.t.) 19.25 g·cm−3 Liquid density at m.p. 17.6 g·cm−3 Melting point 3695 K, 3422 °C, 6192 °F Boiling point 5828 K, 5555 °C, 10031 °F Critical point 13892 K, MPa Heat of fusion 35.3 kJ·mol−1 Heat of vaporization 806.7 kJ·mol−1 Specific heat capacity (25 °C) 24.27 J·mol−1·K−1 Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 3477 3773 4137 4579 5127 5823 Atomic properties Oxidation states 6, 5, 4, 3, 2, 1, 0, −1, -2 (mildly acidic oxide) Electronegativity 2.36 (Pauling scale) Ionization energies 1st: 770 kJ·mol−1 2nd: 1700 kJ·mol−1 Atomic radius 139 pm Covalent radius 162±7 pm Miscellanea Crystal structure body-centered cubic Magnetic ordering paramagnetic2 Electrical resistivity (20 °C) 52.8 nΩ·m Thermal conductivity (300 K) 173 W·m−1·K−1 Thermal expansion (25 °C) 4.5 µm·m−1·K−1 Young's modulus 411 GPa Shear modulus 161 GPa Bulk modulus 310 GPa Poisson ratio 0.28 Mohs hardness 7.5 Vickers hardness 3430 MPa Brinell hardness 2570 MPa CAS registry number 7440-33-7 Most stable isotopes Main article: Isotopes of tungsten iso NA half-life DM DE (MeV) DP 180W 0.12% 1.8×1018 y α 2.516 176Hf 181W syn 121.2 d ε 0.188 181Ta 182W 26.50% 182W is stable with 108 neutrons 183W 14.31% 183W is stable with 109 neutrons 184W 30.64% 184W is stable with 110 neutrons 185W syn 75.1 d β− 0.433 185Re 186W 28.43% 186W is stable with 112 neutrons v · d · e Tungsten ( /ˈtʌŋstən/), also known as wolfram ( /ˈwʊlfrəm/ WOOL-frəm), is a chemical element with the chemical symbol W and atomic number 74. A steel-gray metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Also remarkable is its high density of 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead.3 Tungsten with minor amounts of impurities is often brittle4 and hard, making it difficult to work. However, very pure tungsten is more ductile, and can be cut with a hacksaw.5

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), and superalloys. Tungsten's hardness and high density give it military applications in penetrating projectiles. Tungsten compounds are most often used industrially as catalysts. Tungsten is the only metal from the third transition series that is known to occur in biomolecules, where it is used in a few species of bacteria. It is the heaviest element known to be used by living organisms.67 Contents 1 History 1.1 Etymology 2 Characteristics 2.1 Physical properties 2.2 Isotopes 2.3 Chemical properties 2.4 Occurrence 2.4.1 Biological role 2.4.1.1 Other effects on biochemistry 3 Production 4 Applications 4.1 Hard materials 4.2 Alloys 4.3 Armaments 4.4 Chemical applications 4.5 Niche uses 4.5.1 Electronics 5 Precautions 6 See also 7 References 8 External links History In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from scheelite (at the time named tungstenite). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid.8 In 1783, José and Fausto Elhuyar found an acid made from wolframite that was identical to tungstic acid. Later that year, in Spain, the brothers succeeded in isolating tungsten by reduction of this acid with charcoal, and they are credited with the discovery of the element.910 In World War II, tungsten played a significant role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its deposits of wolframite ore. Tungsten's resistance to high temperatures and its strengthening of alloys made it an important raw material for the arms industry.11 Etymology The name "tungsten" (from the Nordic tung sten, meaning "heavy stone") is used in English, French, and many other languages as the name of the element. Tungsten was the old Swedish name for the mineral scheelite. The other name "wolfram" (or "volfram"), used for example in most European (especially Germanic and Slavic) languages, is derived from the mineral wolframite, and this is also the origin of its chemical symbol, W.5 The name "wolframite" is derived from German "wolf rahm" ("wolf soot" or "wolf cream"), the name given to tungsten by Johan Gottschalk Wallerius in 1747. This, in turn, derives from "Lupi spuma", the name Georg Agricola used for the element in 1546, which translates into English as "wolf's froth" or "cream" (the etymology is not entirely certain), and is a reference to the large amounts of tin consumed by the mineral during its extraction.12 Characteristics Physical properties In tungsten's raw form, it is a steel-gray metal that is often brittle and hard to work, but if pure, it can be worked easily.5 It is worked by forging, drawing, extruding or sintering. Of all metals in pure form, tungsten has the highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure and (at temperatures above 1,650 °C, 3,000 °F) the highest tensile strength.13 Tungsten has the lowest coefficient of thermal expansion of any pure metal. The low thermal expansion and high melting point and strength of tungsten are due to strong covalent bonds formed between tungsten atoms by the 5d electrons.14 Alloying small quantities of tungsten with steel greatly increases its toughness.3 Isotopes Main article: Isotopes of tungsten

Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed15 to do so with a half-life of (1.8 ± 0.2)×1018 yr; on average, this yields about two alpha decays of 180W in one gram of natural tungsten per year.16 The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be16 182W, T1/2 > 8.3×1018 years 183W, T1/2 > 29×1018 years 184W, T1/2 > 13×1018 years 186W, T1/2 > 27×1018 years Another 30 artificial radioisotopes of tungsten have been characterized, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days, 178W with a half-life of 21.6 days, and 187W with a half-life of 23.72 h.16 All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes.16 Tungsten also has 4 meta states, the most stable being 179mW (T½ 6.4 minutes). Chemical properties Main article: Tungsten compounds Elemental tungsten resists attack by oxygen, acids, and alkalis.17 The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from −2 to +6.1718 Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO2− 4. Tungsten carbides (W2C and WC) are produced by heating powdered tungsten with carbon. W2C is resistant to chemical attack, although it reacts strongly with chlorine to form tungsten hexachloride (WCl6).3 In aqueous solution, tungstate gives the heteropoly acids and polyoxometalate anions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion, W7O6– 24, which over time converts to the less soluble "paratungstate B" anion, H2W12O10– 42.19 Further acidification produces the very soluble metatungstate anion, H2W12O6– 40, after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the Keggin anion. Many other polyoxometalate anions exist as metastable species. The inclusion of a different atom such as phosphorus in place of the two central hydrogens in metatungstate produces a wide variety of heteropoly acids, such as phosphotungstic acid H3PW12O40. Tungsten trioxide can form intercalation compounds with alkali metals. These are known as bronzes; an example is sodium tungsten bronze. Occurrence Tungsten is found in the minerals wolframite (iron-manganese tungstate, (Fe,Mn)WO4), scheelite (calcium tungstate, (CaWO4), ferberite (FeWO4) and hübnerite (MnWO4). China produced over 75% of this total in 2000, with most of the remaining production coming from Austria, Bolivia, Portugal, Russia, and Colombia.20 Significant reserves in nations other than the aforementioned producers exist in the United States (3.2% of the estimated global reserve base), Canada (7.9% of the estimated global reserve base), and North Korea (0.56% of the estimated global reserve base). 21 Biological role

Tungsten, at atomic number 74, is the heaviest element known to be biologically functional, with the next heaviest being iodine (Z = 53). Although not in eukaryotes, tungsten is used by some bacteria. For example, enzymes called oxidoreductases use tungsten similarly to molybdenum by using it in a tungsten-pterin complex with molybdopterin (molybdopterin, despite its name, does not contain molybdenum, but may complex with either molybdenum or tungsten in use by living organisms). Tungsten-using enzymes typically reduce carboxylic acids to aldehydes.22 However, the tungsten oxidoreductases may also catalyse oxidations. The first tungsten-requiring enzyme to be discovered also requires selenium, and in this case the tungsten-selenium pair may function analogously to the molybdenum-sulfur pairing of some molybdenum cofactor-requiring enzymes.23 One of the enzymes in the oxidoreductase family which sometimes employ tungsten (bacterial formate dehydrogenase H) is known to use a selenium-molybdenum version of molybdopterin.24 Although a tungsten-containing xanthine dehydrogenase from bacteria has been found to contain tungsten-molydopterin and also non-protein bound selenium, a tungsten-selenium molybdopterin complex has not been definitively described.25 Other effects on biochemistry In soil, tungsten metal oxidizes to the tungstate anion. It may substitute for molybdenum in certain enzymes, and in such cases the resulting enzyme in eukaryotes would presumably be inert. The soil's chemistry determines how the tungsten polymerizes; alkaline soils cause monomeric tungstates; acidic soils cause polymeric tungstates.26 Sodium tungstate and lead have been studied for their effect on earthworms. Lead was found to be lethal at low levels and sodium tungstate was much less toxic, but the tungstate completely inhibited their reproductive ability.27 Tungsten has been studied as a biological copper metabolic antagonist, in a role similar to the action of molybdenum. It has been found that tetrathiotungstates may be used as biological copper chelation chemicals, similar to the tetrathiomolybdates.28 Production Wolframite Tungsten output in 2005 About 37,400 tonnes of tungsten concentrates were produced in the year 2000.20 Tungsten is extracted from its ores in several stages. The ore is eventually converted to tungsten(VI) oxide (WO3), which is heated with hydrogen or carbon to produce powdered tungsten.8 It can be used in that state or pressed into solid bars. Tungsten can also be extracted by hydrogen reduction of WF6: WF6 + 3 H2 → W + 6 HF or pyrolytic decomposition:29 WF6 → W + 3 F2 (ΔHr = +) Tungsten is not traded as a futures contract and cannot be tracked on exchanges like the London Metal Exchange. The price for pure metal is around $20,075 per tonne as of October 2008.30 Applications Close-up of a tungsten filament inside a halogen lamp. Tungsten carbide ring (jewelry)

Approximately half of the tungsten is consumed for the production of hard materials (tungsten carbide), with the remaining major use being its use in alloys and steels. Less than 10% is used in chemical compounds.31 Hard materials Tungsten is mainly used in the production of hard materials based on tungsten carbide, one of the hardest carbides, with a melting point of 2770 °C. WC is an efficient electrical conductor, but W2C is less so. WC is used to make wear-resistant abrasives and cutters and knives for drills, circular saws, milling and turning tools used by the metalworking, woodworking, mining, petroleum and construction industries3 and accounts for about 60% of current tungsten consumption.32 Alloys The hardness and density of tungsten are applied in obtaining heavy metal alloys. A good example is high speed steel, which can contain as much as 18% tungsten.33 Tungsten's high melting point makes tungsten a good material for applications like rocket nozzles, for example in the UGM-27 Polaris Submarine-launched ballistic missile.34 Superalloys containing tungsten, such as Hastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings. Armaments Tungsten, usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium, in applications where uranium's additional pyrophoric properties are not required (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in cannon shells, grenades and missiles, to create supersonic shrapnel. Tungsten has also been used in Dense Inert Metal Explosives, which use it as dense powder to reduce collateral damage while increasing the lethality of explosives within a small radius. 35 Chemical applications Tungsten(IV) sulfide is a high temperature lubricant and is a component of catalysts for hydrodesulfurization. MoS2 is more commonly used for such applications. Tungsten oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting. Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine. Other salts that contain tungsten are used in the chemical and tanning industries.13 Niche uses Applications requiring its high density include heat sinks, weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in race cars for NASCAR and Formula One. It is an ideal material to use as a dolly for riveting, where the mass necessary for good results can be achieved in a compact bar. High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts36 (to allow for a smaller diameter and thus tighter groupings) or for fishing lures (tungsten beads allow the fly to sink rapidly). Some types of strings for musical instruments are wound with tungsten wires.

Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to gold or platinum.537 Its hardness makes it ideal for rings that will resist scratching, are hypoallergenic, and will not need polishing, which is especially useful in designs with a brushed finish.38 Electronics Because it retains its strength at high temperatures and has a high melting point, elemental tungsten is used in many high-temperature applications,39 such as light bulb, cathode-ray tube, and vacuum tube filaments, heating elements, and rocket engine nozzles.5 Its high melting point also makes tungsten suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, notably in the gas tungsten arc welding process (also called tungsten inert gas (TIG) welding). Because of its conductive properties and relative chemical inertia, tungsten is also used in electrodes, and in the emitter tips in electron-beam instruments that use field emission guns, such as electron microscopes. In electronics, tungsten is used as an interconnect material in integrated circuits, between the silicon dioxide dielectric material and the transistors. It is used in metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (or molybdenum) on silicon.29 The electronic structure of tungsten makes it one of the main sources for X-ray targets,40 and also for shielding from high-energy radiations (such as in the radiopharmaceutical industry for shielding radioactive samples of FDG). Tungsten powder is used as a filler material in plastic composites, which are used as a nontoxic substitute for lead in bullets, shot, and radiation shields. Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals.13 Precautions Because tungsten is rare and its compounds generally inert, the effects of tungsten on the environment are limited.41 The median lethal dose LD50 depends strongly on the animal and the method of administration and varies between 59 mg/kg (intravenous, rabbit)4243 and 5000 mg/kg (tungsten metal powder, intraperitoneal, rats).4445 See also Field emission gun Isotopes of tungsten References ^ "Why does Tungsten not 'Kick' up an electron from the s sublevel ?". http://www.madsci.org/posts/archives/2000-02/951518136.Ch.r.html. Retrieved 2008-06-15.  ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press. ^ a b c d Daintith, John (2005). Facts on File Dictionary of Chemistry (4th ed.). New York: Checkmark Books. ISBN 0816056498.  ^ Lassner, Erik; Schubert, Wolf-Dieter (1999). "low temperature brittleness". Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds. Springer. p. 256. ISBN 9780306450532. http://books.google.com/?id=foLRISkt9gcC&pg=PA20.  ^ a b c d e Stwertka, Albert (2002). A Guide to the elements (2nd ed.). New York: Oxford University Press. ISBN 0195150260.  ^ McMaster, J. and Enemark, John H (1998). "The active sites of molybdenum- and tungsten-containing enzymes". Current Opinion in Chemical Biology 2 (2): 201–207. doi:10.1016/S1367-5931(98)80061-6. PMID 9667924.  ^ Hille, Russ (2002). "Molybdenum and tungsten in biology". Trends in Biochemical Sciences 27 (7): 360–367. doi:10.1016/S0968-0004(02)02107-2. PMID 12114025.  ^ a b Saunders, Nigel (February 2004). Tungsten and the Elements of Groups 3 to 7 (The Periodic Table). Chicago, Illinois: Heinemann Library. ISBN 1403435189.  ^ "ITIA Newsletter" (PDF). International Tungsten Industry Association. 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V. et al. (1998). "Selenium-Containing Formate Dehydrogenase H from Escherichia coli: A Molybdopterin Enzyme That Catalyzes Formate Oxidation without Oxygen Transfer". Biochemistry 37 (10): 3518–3528. doi:10.1021/bi972177k. PMID 9521673.  ^ Schrader, Thomas; Rienhofer, Annette; Andreesen, Jan R. (1999). "Selenium-containing xanthine dehydrogenase from Eubacterium barkeri". Eur. J. Biochem. 264 (3): 862–71. doi:10.1046/j.1432-1327.1999.00678.x. PMID 10491134.  ^ Chemical & Engineering News, 19 Jan. 2009, "Unease over Tungsten", p. 63 ^ Inouye, L. S. et al. (2006). "Tungsten effects on survival, growth, and reproduction in the earthworm, eisenia fetida". Environmental Toxicology & Chemistry 25 (3): 763. doi:10.1897/04-578R.1.  ^ McQuaid A; Lamand M; Mason J. (1994). "Thiotungstate-copper interactions II. The effects of tetrathiotungstate on systemic copper metabolism in normal and copper-treated rats". J Inorg Biochem 53: 205. doi:10.1016/0162-0134(94)80005-7.  ^ a b Schey, John A. (1987). Introduction to Manufacturing Processes, 2nd ed.. McGraw-Hill, Inc.  ^ "Metal Bulletin". http://www.mineralprices.com. Retrieved 2009-05-05.  ^ Erik Lassner, Wolf-Dieter Schubert, Eberhard Lüderitz, Hans Uwe Wolf, "Tungsten, Tungsten Alloys, and Tungsten Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. doi:10.1002/14356007.a27_229. ^ "The Canadian Encyclopaedia". http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=A1ARTA0008159. Retrieved 2009-05-05.  ^ "Tungsten Applications - Steel". azom.com. 2000–2008. http://www.azom.com/details.asp?ArticleID=1264. Retrieved 2008-06-18.  ^ Ramakrishnan, P. (2007-01-01). "Powder metallurgyfor Aerospace Applications". Powder metallurgy : processing for automotive, electrical/electronic and engineering industry. New Age International. p. 38. ISBN 8122420303. http://books.google.com/?id=9n-rX13bNsAC&pg=PA38.  ^ Dense Inert Metal Explosive (DIME) ^ Turrell, Kerry (2004). Tungsten. Marshall Cavendish. p. 24. ISBN 0761415483. http://books.google.com/?id=QUyO7jgvOQUC&pg=PA24.  ^ Hesse, Rayner W. (2007). "tungsten". Jewelrymaking through history : an encyclopedia. Westport, Conn.: Greenwood Press. pp. 190–192. ISBN 9780313335075. http://books.google.com/?id=DIWEi5Hg93gC&pg=PA190.  ^ Gray, Theo (March 14, 2008). "How to Make Convincing Fake-Gold Bars". Popular Science. http://www.popsci.com/diy/article/2008-03/how-make-convincing-fake-gold-bars. Retrieved 2008-06-18.  ^ DeGarmo, E. Paul (1979). Materials and Processes in Manufacturing, 5th ed.. New York: MacMillan Publishing.  ^ Hasz, Wayne Charles et al. "X-ray target" U.S. Patent 6,428,904, August 6, 2002 ^ Strigul, N; Koutsospyros, A; Arienti, P; Christodoulatos, C; Dermatas, D; Braida, W (Oct 2005). "Effects of tungsten on environmental systems.". Chemosphere 61 (2): 248–58. doi:10.1016/j.chemosphere.2005.01.083. ISSN 0045-6535. PMID 16168748.  ^ Koutsospyros, A.; Braida, W.; Christodoulatos, C.; Dermatas, D.; Strigul, N. (2006). "A review of tungsten: From environmental obscurity to scrutiny". Journal of Hazardous Materials 136 (1): 1–19. doi:10.1016/j.jhazmat.2005.11.007. PMID 16343746.  ^ Lagarde, F; Leroy, M (2002). "Metabolism and toxicity of tungsten in humans and animals.". Metal ions in biological systems 39: 741–59. PMID 11913143.  also reported in Astrid Sigel, Helmut Sigel (2002). Molybdenum and tungsten: their roles in biological processes. CRC Press. p. 741 ff. ISBN 0824707656. http://books.google.com/?id=2yNCBzFQgMgC&pg=PA741&lpg=PA741.  ^ Masten, Scott (2003). "Tungsten and Selected Tungsten Compounds — Review of Toxicological Literature". National Institute of Environmental Health Sciences. http://ntp.niehs.nih.gov/ntp/htdocs/Chem_Background/ExSumPdf/tungsten.pdf. Retrieved 2009-03-19.  ^ Marquet, P. et al. (1997). "Tungsten determination in biological fluids, hair and nails by plasma emission spectrometry in a case of severe acute intoxication in man.". Journal of forensic sciences 42 (3): 527–30. PMID 9144946.  External links Wikimedia Commons has media related to: Tungsten Look up tungsten in Wiktionary, the free dictionary. WebElements.com – Tungsten Properties, Photos, History, MSDS Picture in the collection from Heinrich Pniok Elementymology & Elements Multidict by Peter van der Krogt – Tungsten Detection of the Natural Alpha Decay of Tungsten International Tungsten Industry Association v · d · e Periodic table H   He Li Be   B C N O F Ne Na Mg   Al Si P S Cl Ar K Ca   Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr   Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Uuq Uup Uuh Uus Uuo Alkali metals Alkaline earth metals Lanthanides Actinides Transition metals Other metals Metalloids Other nonmetals Halogens Noble gases Unknown chem. properties Large version