Editing Tungsten (section)

===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>