Editing Group 5 element (section)

==== Oxides ====
Vanadium forms oxides in the +2, +3, +4 and +5 [[oxidation state]]s, forming [[vanadium(II) oxide]] (VO), [[vanadium(III) oxide]] (V<sub>2</sub>O<sub>3</sub>), [[vanadium(IV) oxide]] (VO<sub>2</sub>) and [[vanadium(V) oxide]] (V<sub>2</sub>O<sub>5</sub>). Vanadium(V) oxide or vanadium pentoxide is the most common, being precursor to most alloys and compounds of vanadium, and is also a widely used industrial catalyst.<ref name=Ullmann>{{Cite book|doi = 10.1002/14356007.a27_367|chapter = Vanadium and Vanadium Compounds|title = Ullmann's Encyclopedia of Industrial Chemistry|year = 2000|last1 = Bauer|first1 = Günter|last2 = Güther|first2 = Volker|last3 = Hess|first3 = Hans|last4 = Otto|first4 = Andreas|last5 = Roidl|first5 = Oskar|last6 = Roller|first6 = Heinz|last7 = Sattelberger|first7 = Siegfried|isbn = 3527306730}}</ref>

Niobium forms oxides in the oxidation states +5 ([[Niobium pentoxide|{{chem2|Nb2O5}}]]),<ref>{{Cite web|url=https://pubchem.ncbi.nlm.nih.gov/compound/Niobium_oxide#section=Top|title=Niobium oxide {{!}} Nb2O5 – PubChem|last=Pubchem|website=pubchem.ncbi.nlm.nih.gov|access-date=29 June 2016|archive-date=16 August 2016|archive-url=https://web.archive.org/web/20160816070526/https://pubchem.ncbi.nlm.nih.gov/compound/Niobium_oxide#section=Top|url-status=live}}</ref> +4 ([[Niobium dioxide|{{chem2|NbO2}}]]), and the rarer oxidation state, +2 ([[niobium monoxide|NbO]]).<ref name=Greenwood&Earnshaw2nd /> Most common is the pentoxide, also being precursor to almost all niobium compounds and alloys.<ref name="HollemanAF" /><ref name="Cardarelli">{{cite book|first = Francois|last = Cardarelli|date = 2008|title = Materials Handbook |publisher = Springer London|isbn = 978-1-84628-668-1}}</ref>

[[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 name="Greenwood&Earnshaw2nd">{{Greenwood&Earnshaw2nd}}</ref>
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