Editing Group 5 element (section)

=== Tantalum ===

Tantalum is dark (blue-gray),<ref>{{cite book | chapter = Tantalum | chapter-url = https://books.google.com/books?id=5o3Lr2Swz8sC&pg=PA204 | isbn = 978-0-86516-573-1 | title = Classical Mythology & More: A Reader Workbook | author1 = Colakis, Marianthe | author2 = Masello, Mary Joan | date = 2007-06-30| publisher=Bolchazy-Carducci Publishers }}</ref> dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to [[corrosion]] by [[acid]]s; in fact, at temperatures below 150&nbsp;°[[Celsius|C]] tantalum is almost completely immune to attack by the normally aggressive [[aqua regia]]. It can be dissolved with [[hydrofluoric acid]] or acidic solutions containing the [[fluoride]] ion and [[sulfur trioxide]], as well as with a solution of [[potassium hydroxide]]. Tantalum's high melting point of 3017&nbsp;°C (boiling point 5458&nbsp;°C) is exceeded among the elements only by [[tungsten]],<ref name="desu">{{cite book |author=Hammond, C. R. |url=https://archive.org/details/crchandbookofche81lide |title=The Elements, in Handbook of Chemistry and Physics |date=2004 |publisher=CRC press |isbn=978-0-8493-0485-9 |edition=81st |url-access=registration}}</ref> [[rhenium]]<ref name="Zhang2011">{{Cite journal |last=Zhang |first=Yiming |date=2011-01-11 |title=Corrected Values for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks |url=https://www.researchgate.net/publication/231538496 |journal=Journal of Chemical & Engineering Data |volume=56 |url-access=<!--WP:URLACCESS-->}}</ref> [[osmium]],<ref>{{cite book |last1=Rumble |first1=John R. |title=CRC Handbook of Chemistry and Physics: A Ready Reference Book of Chemical and Physical Data |last2=Bruno |first2=Thomas J. |last3=Doa |first3=Maria J. |date=2022 |publisher=CRC Press |isbn=978-1-032-12171-0 |edition=103rd |location=Boca Raton, FL |page=40 |chapter=Section 4: Properties of the Elements and Inorganic Compounds}}</ref> and [[carbon]].<ref name="triple">{{cite journal |last=Greenville Whittaker |first=A. |date=1978 |title=The controversial carbon solid−liquid−vapour triple point |journal=Nature |volume=276 |issue=5689 |pages=695–696 |bibcode=1978Natur.276..695W |doi=10.1038/276695a0 |s2cid=4362313}}</ref>    

Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relatively [[Ductility|ductile]] and soft; it has [[body-centered cubic]] structure ([[space group]] ''Im3m'', lattice constant ''a'' = 0.33058&nbsp;nm), [[Knoop hardness test|Knoop hardness]] 200–400 HN and electrical resistivity 15–60 μΩ⋅cm. The beta phase is hard and brittle; its crystal symmetry is [[tetragonal]] (space group ''P42/mnm'', ''a'' = 1.0194&nbsp;nm, ''c'' = 0.5313&nbsp;nm), Knoop hardness is 1000–1300 HN and electrical resistivity is relatively high at 170–210 μΩ⋅cm. The beta phase is metastable and converts to the alpha phase upon heating to 750–775&nbsp;°C. Bulk tantalum is almost entirely alpha phase, and the beta phase usually exists as thin films<ref>{{cite journal|title=Electronic structure of β-Ta films from X-ray photoelectron spectroscopy and first-principles calculations|date=2019|last1=Magnuson|first1=M.|journal=Applied Surface Science|volume=470|pages=607–612|last2=Greczynski|first2=G.|last3=Eriksson|first3=F.|last4=Hultman|first4=L.|last5=Hogberg|first5=H.|doi=10.1016/j.apsusc.2018.11.096|url=http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152876|bibcode=2019ApSS..470..607M|s2cid=54079998}}</ref> obtained by magnetron
[[sputtering]], [[chemical vapor deposition]] or [[Electrochemistry|electrochemical deposition]] from a [[Eutectic system|eutectic]] molten salt solution.<ref>{{cite journal|doi=10.1016/j.surfcoat.2003.06.008|title=Texture, structure and phase transformation in sputter beta tantalum coating|date=2004|last1=Lee|first1=S.|journal=Surface and Coatings Technology|volume=177– 178|page=44|last2=Doxbeck|first2=M.|last3=Mueller|first3=J.|last4=Cipollo|first4=M.|last5=Cote|first5=P.|url=https://zenodo.org/record/1259369}}</ref>