Editing Tantalum (section)

==Chemical compounds==
Tantalum forms compounds in oxidation states −3 to +5. Most commonly encountered are oxides of Ta(V), which includes all minerals. The chemical properties of Ta and Nb are very similar. In aqueous media, Ta only exhibits the +5 oxidation state. Like niobium, tantalum is barely soluble in dilute solutions of [[Hydrochloric acid|hydrochloric]], [[Sulfuric acid|sulfuric]], [[Nitric acid|nitric]] and [[phosphoric acid]]s due to the precipitation of hydrous Ta(V) oxide.<ref name="Aguly" /> In basic media, Ta can be solubilized due to the formation of polyoxotantalate species.<ref>{{Cite journal|last1=Deblonde|first1=Gauthier J. -P.|last2=Chagnes|first2=Alexandre|last3=Bélair|first3=Sarah|last4=Cote|first4=Gérard|date=2015-07-01|title=Solubility of niobium(V) and tantalum(V) under mild alkaline conditions|journal=Hydrometallurgy|volume=156|pages=99–106|doi=10.1016/j.hydromet.2015.05.015|bibcode=2015HydMe.156...99D |issn=0304-386X}}</ref>

===Oxides, nitrides, carbides, sulfides===
[[Tantalum pentoxide]] (Ta<sub>2</sub>O<sub>5</sub>) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including many [[defect structure]]s, and are lightly studied or poorly characterized.<ref>{{Greenwood&Earnshaw2nd}}</ref>

Tantalates, compounds containing [TaO<sub>4</sub>]<sup>3−</sup> or [TaO<sub>3</sub>]<sup>−</sup> are numerous. [[Lithium tantalate]] (LiTaO<sub>3</sub>) adopts a perovskite structure. [[Lanthanum]] tantalate (LaTaO<sub>4</sub>) contains isolated {{chem|TaO|4|3−}} tetrahedra.<ref name="HollemanAF">{{cite book|title=Lehrbuch der Anorganischen Chemie|date=2007|publisher=de Gruyter|isbn=978-3-11-017770-1|edition=102nd|language=de|author=Holleman, A. F.|author2=Wiberg, E.|author3=Wiberg, N.}}</ref>

As in the cases of other [[refractory metal]]s, the hardest known compounds of tantalum are nitrides and carbides. [[Tantalum carbide]], TaC, like the more commonly used [[tungsten carbide]], is a hard [[ceramic]] that is used in cutting tools. Tantalum(III) nitride is used as a thin film insulator in some microelectronic fabrication processes.<ref>{{cite journal|title=Microstructure of amorphous tantalum nitride thin films|first=S.|last=Tsukimoto| author2= Moriyama, M.| author3= Murakami, Masanori| journal=Thin Solid Films|date=1961|volume= 460|issue=1–2|pages=222–226|doi=10.1016/j.tsf.2004.01.073|bibcode = 2004TSF...460..222T }}</ref>

The best studied chalcogenide is [[Tantalum(IV) sulfide|Tantalum sulfide]] (TaS<sub>2</sub>), a layered [[semiconductor]], as seen for other [[transition metal dichalcogenide]]s. A tantalum-tellurium alloy forms [[quasicrystal]]s.<ref name="HollemanAF" />

===Halides===
Tantalum halides span the oxidation states of +5, +4, and +3. [[Tantalum pentafluoride]] (TaF<sub>5</sub>) is a white solid with a melting point of 97.0&nbsp;°C. The anion [TaF<sub>7</sub>]<sup>2-</sup> is used for its separation from niobium.<ref name="ICE">{{cite journal|title=Staff-Industry Collaborative Report: Tantalum and Niobium|first=Donald J.|last=Soisson|author2=McLafferty, J. J. |author3=Pierret, James A. | journal=Ind. Eng. Chem.|date=1961|volume= 53|issue=11|pages=861–868|doi=10.1021/ie50623a016}}</ref> The chloride [[tantalum(V) chloride|{{chem|TaCl|5}}]], which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to an [[oxychloride]]. The lower halides {{chem|TaX|4}} and {{chem|TaX|3}}, feature Ta-Ta bonds.<ref name="HollemanAF" /><ref name="Aguly">{{cite book|first=Anatoly|last=Agulyansky|title=The Chemistry of Tantalum and Niobium Fluoride Compounds|publisher=Elsevier|date=2004| isbn=978-0-444-51604-6| url=https://books.google.com/books?id=Z-4QXNB5Hp8C|access-date=2008-09-02}}</ref>

===Organotantalum compounds===
[[Organotantalum chemistry|Organotantalum compound]]s include [[pentamethyltantalum]], mixed alkyltantalum chlorides, alkyltantalum hydrides, alkylidene complexes, as well as cyclopentadienyl derivatives of the same.<ref name="Schrock">{{Cite journal|last=Schrock|first=Richard R.|date=1979-03-01|title=Alkylidene complexes of niobium and tantalum|journal=Accounts of Chemical Research|volume=12|issue=3|pages=98–104|doi=10.1021/ar50135a004|issn=0001-4842}}</ref><ref>{{cite journal|doi=10.1021/om701189e|title=Ethylene Complexes of the Early Transition Metals: Crystal Structures of {{chem|[HfEt|4|(C|2|H|4|)|2-|]}} and the Negative-Oxidation-State Species {{chem|[TaHEt(C|2|H|4|)|3|3-|]}} and {{chem|[WH(C|2|H|4|)|4|3-|]}}|author=Morse, P. M.|journal=Organometallics|date=2008|volume=27|issue=5|page=984|display-authors=1|author2=Shelby, Q. D. |author3=Kim, D. Y. |author4=Girolami, G. S. |name-list-style=amp}}</ref> Diverse salts and substituted derivatives are known for the hexacarbonyl [Ta(CO)<sub>6</sub>]<sup>−</sup> and related [[isocyanide]]s.
[[File:DOSBIWoneRotamer.png|144px|thumb|Ta(CH<sub>3</sub>)<sub>5</sub>.]]