Editing Tungsten (section)

==Characteristics==

===Physical properties===
In its raw form, tungsten is a hard steel-grey [[metal]] that is often [[brittle]] and hard to [[metalworking|work]]. Purified, monocrystalline tungsten retains its [[hardness]] (which exceeds that of many steels), and becomes [[malleable]] enough that it can be worked easily.<ref name="albert" /> It is worked by [[forging]], [[drawing (manufacturing)|drawing]], or [[extrusion|extruding]] but it is more commonly formed by [[sintering]]. Sintering is often used due to the very high melting point of tungsten.

Of all metals in pure form, tungsten has the highest [[melting point]] ({{cvt|3422|C|F|disp=comma}}), lowest [[vapor pressure]] (at temperatures above {{cvt|1650|C|F|disp=comma}}), and the highest [[tensile strength]].<ref name="desu">{{cite book| author = Hammond, C. R.| title = The Elements, in Handbook of Chemistry and Physics| edition = 81st| publisher = CRC press| isbn = 978-0-8493-0485-9| date = 2004| url-access = registration| url = https://archive.org/details/crchandbookofche81lide}}</ref> Although [[carbon]] remains solid at higher temperatures than tungsten, carbon [[sublimation (phase transition)|sublimes]] at [[atmospheric pressure]] instead of melting, so it has no melting point. Moreover, tungsten's most stable [[crystal phase]] does not exhibit any high-pressure-induced structural transformations for pressures up to at least 364 gigapascals.<ref>{{Cite journal |last1=McMahon |first1=Malcolm I. |last2=Nelmes |first2=Richard J.|author2-link=Richard Nelmes|date=2006 |title=High-pressure structures and phase transformations in elemental metals |url=http://xlink.rsc.org/?DOI=b517777b |journal=Chemical Society Reviews |language=en |volume=35 |issue=10 |pages=943–963 |doi=10.1039/b517777b |pmid=17003900 |issn=0306-0012}}</ref> Tungsten has the lowest [[coefficient of thermal expansion]] of any pure metal. The low thermal expansion and high melting point and [[tensile strength]] of tungsten originate from strong [[covalent bond]]s<!--YES REALLY, THEY ARE QUITE DIRECTIONAL--> formed between tungsten atoms by the 5d electrons.<ref>{{cite book|url=https://books.google.com/books?id=foLRISkt9gcC&pg=PA9|page=9|title=Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds|author=Lassner, Erik |author2=Schubert, Wolf-Dieter |publisher=Springer|date=1999|isbn=978-0-306-45053-2}}</ref>
Alloying small quantities of tungsten with [[steel]] greatly increases its [[toughness]].<ref name="daintith" />

Tungsten exists in two major [[crystallinity|crystalline]] forms: α and β. The former has a [[body-centered cubic]] structure and is the more stable form. The structure of the [[beta-tungsten|β phase]] is called [[A15 phases|A15 cubic]]; it is [[metastable]], but can coexist with the α phase at ambient conditions owing to non-equilibrium synthesis or stabilization by impurities. Contrary to the α phase which crystallizes in isometric grains, the β form exhibits a columnar [[Crystal habit|habit]]. The α phase has one third of the [[electrical resistivity]]<ref>Bean, Heather (October 19, 1998). [https://web.archive.org/web/20111023221423/http://users.frii.com/bean/analysis.htm Material Properties and Analysis Techniques for Tungsten Thin Films]. frii.com</ref> and a much lower [[superconductivity|superconducting transition temperature]] T<sub>C</sub> relative to the β phase: ca. 0.015 K vs. 1–4 K; mixing the two phases allows obtaining intermediate T<sub>C</sub> values.<ref>{{cite journal|title=Tuning of Tungsten Thin Film Superconducting Transition Temperature for Fabrication of Photon Number Resolving Detectors|url=http://mysite.du.edu/~balzar/IEEE-Adriana%20-2005.pdf|author=Lita, A. E.|author2=Rosenberg, D.|author3=Nam, S.|author4=Miller, A.|author5=Balzar, D.|author6=Kaatz, L. M.|author7=Schwall, R. E.|journal=IEEE Transactions on Applied Superconductivity|volume=15|issue=2|pages=3528–3531|doi=10.1109/TASC.2005.849033|date=2005|url-status=live|archive-url=https://web.archive.org/web/20130513015735/http://mysite.du.edu/~balzar/IEEE-Adriana%20-2005.pdf|archive-date=2013-05-13|bibcode=2005ITAS...15.3528L|s2cid=5804011}}</ref><ref>{{Cite journal| doi = 10.1103/PhysRevLett.16.101| volume = 16 | issue = 3| pages = 101–104| last = Johnson| first = R. T.|author2=O. E. Vilches |author3=J. C. Wheatley |author4=Suso Gygax | title = Superconductivity of Tungsten| journal = Physical Review Letters| date = 1966|bibcode = 1966PhRvL..16..101J }}</ref> The T<sub>C</sub> value can also be raised by [[alloy]]ing tungsten with another metal (e.g. 7.9 K for W-[[technetium|Tc]]).<ref>{{Cite journal | doi = 10.1103/PhysRev.140.A1177| volume = 140| issue = 4A| pages = A1177–A1180| last = Autler| first = S. H.|author2=J. K. Hulm |author3=R. S. Kemper | title = Superconducting Technetium–Tungsten Alloys| journal = Physical Review|date = 1965|bibcode = 1965PhRv..140.1177A }}</ref> Such tungsten alloys are sometimes used in low-temperature superconducting circuits.<ref>{{Cite journal | doi = 10.1209/0295-5075/79/57008| volume = 79| page = 57008| last = Shailos| first = A.|author2=W Nativel |author3=A Kasumov |author4=C Collet |author5=M Ferrier |author6=S Guéron |author7=R Deblock |author8=H Bouchiat |author8-link= Hélène Bouchiat | title = Proximity effect and multiple Andreev reflections in few-layer graphene| journal = Europhysics Letters| date = 2007|arxiv = cond-mat/0612058 |bibcode = 2007EL.....7957008S | issue = 5 | s2cid = 119351442}}</ref><ref>{{Cite journal| doi = 10.1103/PhysRevB.72.033414| volume = 72| issue = 3| page = 033414| last = Kasumov| first = A. Yu.| author2 = K. Tsukagoshi| author3 = M. Kawamura| author4 = T. Kobayashi| author5 = Y. Aoyagi| author6 = K. Senba| author7 = T. Kodama| author8 = H. Nishikawa| author9 = I. Ikemoto| author10 = K. Kikuchi| author11 = V. T. Volkov| author12 = Yu. A. Kasumov| author13 = R. Deblock| author14 = S. Guéron| author15 = H. Bouchiat|author15-link= Hélène Bouchiat | title = Proximity effect in a superconductor-metallofullerene-superconductor molecular junction| journal = Physical Review B|date=2005|arxiv = cond-mat/0402312 |bibcode = 2005PhRvB..72c3414K | s2cid = 54624704}}</ref><ref>{{Cite journal
| doi = 10.1103/PhysRevB.35.8850 | pmid = 9941272| volume = 35| issue = 16| pages = 8850–8852| last = Kirk| first = M. D.| author2 = D. P. E. Smith| author3 = D. B. Mitzi| author4 = J. Z. Sun| author5 = D. J. Webb| author6 = K. Char| author7 = M. R. Hahn| author8 = M. Naito| author9 = B. Oh| author10 = M. R. Beasley| author11 = T. H. Geballe| author12 = R. H. Hammond| author13 = A. Kapitulnik| author14 = C. F. Quate| title = Point-contact electron tunneling into the high-T_{c} superconductor Y-Ba-Cu-O| journal = Physical Review B| date= 1987|bibcode = 1987PhRvB..35.8850K }}</ref>

===Isotopes===
{{Main|Isotopes of tungsten}}
Naturally occurring tungsten consists of four stable [[isotope]]s (<sup>182</sup>W, <sup>183</sup>W, <sup>184</sup>W, and <sup>186</sup>W) and one very long-lived radioisotope, <sup>180</sup>W. Theoretically, all five can decay into isotopes of element 72 ([[hafnium]]) by [[alpha emission]], but only <sup>180</sup>W has been observed to do so, with a half-life of {{val|1.8e18|0.2}} years;<ref>{{cite journal| author = Danevich, F. A. | display-authors = etal| title = α activity of natural tungsten isotopes| journal = Phys. Rev. C|volume = 67| issue = 1|page = 014310|date = 2003| arxiv = nucl-ex/0211013|doi = 10.1103/PhysRevC.67.014310|bibcode = 2003PhRvC..67a4310D | s2cid = 6733875}}</ref><ref>{{cite journal| author = Cozzini, C. | display-authors = etal| title = Detection of the natural α decay of tungsten| journal = Phys. Rev. C|volume = 70| issue = 6|page = 064606|date = 2004| arxiv = nucl-ex/0408006|doi = 10.1103/PhysRevC.70.064606|bibcode = 2004PhRvC..70f4606C | s2cid = 118891861}}</ref> on average, this yields about two alpha decays of <sup>180</sup>W per gram of natural tungsten per year.<ref name="isotopes">{{cite web|url=http://www.nndc.bnl.gov/chart/|title=Interactive Chart of Nuclides|publisher=Brookhaven National Laboratory|author=Sonzogni, Alejandro|location=National Nuclear Data Center|access-date=2008-06-06|url-status=live|archive-url=https://web.archive.org/web/20080522125027/http://www.nndc.bnl.gov/chart|archive-date=2008-05-22}}</ref> This rate is equivalent to a [[specific activity]] of roughly 63 micro-[[becquerel (unit)|becquerel]] per kilogram. This rate of decay is orders of magnitude lower than that observed in carbon or potassium as found on earth, which likewise contain small amounts of long-lived radioactive isotopes. [[Bismuth]] was long thought to be non-radioactive, but {{chem|209|Bi}} (its longest lived isotope) actually decays with a half life of {{val|2.01e19}} years or about a factor 10 slower than {{chem|180|W}}. However, due to naturally occurring bismuth being 100% {{chem|209|Bi}}, its specific activity is actually higher than that of natural tungsten at 3 milli-becquerel per kilogram. The other naturally occurring isotopes of tungsten have not been observed to decay, constraining their half-lives to be at least {{val|4|e=21|u=years}}.

Another 34 artificial [[radioisotope]]s of tungsten have been characterized, the most stable of which are <sup>181</sup>W with a half-life of 121.2&nbsp;days, <sup>185</sup>W with a half-life of 75.1&nbsp;days, <sup>188</sup>W with a half-life of 69.4&nbsp;days, <sup>178</sup>W with a half-life of 21.6&nbsp;days, and <sup>187</sup>W with a half-life of 23.72 h.<ref name="isotopes" /> All of the remaining [[radioactive]] isotopes have half-lives of less than 3&nbsp;hours, and most of these have half-lives below 8&nbsp;minutes.<ref name="isotopes" /> Tungsten also has 12&nbsp;[[meta state]]s, with the most stable being <sup>179m</sup>W (''t''<sub>1/2</sub>&nbsp;6.4&nbsp;minutes).

===Chemical properties===
Tungsten is a mostly non-reactive element: it does not react with water, is immune to attack by most acids and bases, and does not react with oxygen or air at room temperature.  At elevated temperatures (i.e., when red-hot) it reacts with oxygen to form the [[trioxide]] compound tungsten(VI), WO<sub>3</sub>.  It will, however, react directly with fluorine (F<sub>2</sub>) at room temperature to form [[tungsten hexafluoride|tungsten(VI) fluoride]] (WF<sub>6</sub>), a colorless gas. At around 250&nbsp;°C it will react with chlorine or bromine, and under certain hot conditions will react with iodine.  Finely divided tungsten is [[pyrophoric]].<ref>{{cite web|title=Tungsten: reactions of elements|url=https://www.webelements.com/tungsten/chemistry.html}}</ref><ref name="emsley" />

The most common formal [[oxidation state]] of tungsten is +6, but it exhibits all oxidation states from −2 to +6.<ref name="emsley">{{cite book |last=Emsley |first=John E. |title=The elements |edition=2nd |publisher=Oxford University Press |location=New York |date=1991 |isbn=978-0-19-855569-8 }}</ref><ref>{{Cite journal
| last1 = Morse|first1 = P. M.
| last2 = Shelby|first2 = Q. D.
| last3 = Kim|first3 = D. Y.
| last4 = Girolami|first4 = G. S.
| title = Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt<sub>4</sub>(C<sub>2</sub>H<sub>4</sub>)<sup>2−</sup>] and the Negative-Oxidation-State Species [TaHEt(C<sub>2</sub>H<sub>4</sub>)<sub>3</sub><sup>3−</sup>] and [WH(C<sub>2</sub>H<sub>4</sub>)<sub>4</sub><sup>3−</sup>]
| journal = Organometallics
| volume = 27
| issue = 5
| pages = 984–993
| date = 2008
| doi = 10.1021/om701189e
}}</ref> Tungsten typically combines with oxygen to form the yellow [[tungsten trioxide|tungstic oxide]], WO<sub>3</sub>, which dissolves in aqueous alkaline solutions to form tungstate ions, {{chem|WO|4|2-}}.

[[Tungsten carbide]]s (W<sub>2</sub>C and WC) are produced by heating powdered tungsten with carbon. W<sub>2</sub>C is resistant to chemical attack, although it reacts strongly with [[chlorine]] to form [[tungsten hexachloride]] (WCl<sub>6</sub>).<ref name="daintith" />

In aqueous solution, tungstate gives the [[heteropoly acid]]s and [[polyoxometalate]] [[anion]]s under neutral and acidic conditions. As [[tungstate]] is progressively treated with acid, it first yields the soluble, [[metastable]] "paratungstate A" [[anion]], {{chem|W}}{{su|b=7}}{{chem|O}}{{su|b=24|p=6−}}, which over time converts to the less soluble "paratungstate B" anion, {{chem|H}}{{su|b=2}}{{chem|W}}{{su|b=12}}{{chem|O}}{{su|b=42|p=10−}}.<ref name="SmithBJ">{{cite journal |doi=10.1071/CH00140 |last1=Smith |first1=Bradley J. |last2=Patrick |date=2000 |first2=Vincent A. |title=Quantitative Determination of Sodium Metatungstate Speciation by 183W N.M.R. Spectroscopy |journal=Australian Journal of Chemistry |page=965 |volume=53 |issue=12}}</ref> Further acidification produces the very soluble metatungstate anion, {{chem|H}}{{su|b=2}}{{chem|W}}{{su|b=12}}{{chem|O}}{{su|b=40|p=6−}}, after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-[[oxygen]] [[octahedron|octahedra]] known as the [[Keggin structure|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 [[hydrogen]]s in metatungstate produces a wide variety of heteropoly acids, such as [[phosphotungstic acid]] H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub>.

Tungsten trioxide can form [[intercalation (chemistry)|intercalation]] compounds with alkali metals. These are known as ''bronzes''; an example is [[sodium tungsten bronze]].

In gaseous form, tungsten forms the diatomic species W<sub>2</sub>.  These molecules feature a [[sextuple bond]] between tungsten atoms &mdash; the highest known bond order among [[radioactivity|stable]] atoms.<ref>{{Cite journal|last1=Borin|first1=Antonio Carlos|last2=Gobbo|first2=João Paulo|last3=Roos|first3=Björn O.|date=January 2008|title=A theoretical study of the binding and electronic spectrum of the Mo2 molecule|journal=Chemical Physics|volume=343|issue=2–3|pages=210–216|doi=10.1016/j.chemphys.2007.05.028|issn=0301-0104|bibcode=2008CP....343..210B}}</ref><ref name="Roos">{{cite journal|last1=Roos|first1=Björn O.|last2=Borin|first2=Antonio C.|author3=Laura Gagliardi|year=2007|title=Reaching the Maximum Multiplicity of the Covalent Chemical Bond|url=https://www.academia.edu/13598187|journal=[[Angew. Chem. Int. Ed.]]|volume=46|issue=9|pages=1469–72|doi=10.1002/anie.200603600|pmid=17225237}}</ref>