Editing Group 5 element (section)

== Physical properties ==

The trends in group 5 follow those of the other early d-block groups and reflect the addition of a filled f-shell into the core in passing from the fifth to the sixth period. All the stable members of the group are silvery-blue [[refractory metal]]s, though impurities of [[carbon]], [[nitrogen]], and oxygen make them brittle.<ref name=Greenwood956>{{Greenwood&Earnshaw2nd|page=956-958}}</ref> They all crystallize in the [[cubic crystal system|body-centered cubic]] structure at room temperature,<ref name=Greenwood946>{{Greenwood&Earnshaw2nd|page=946-948}}</ref> and dubnium is expected to do the same.<ref name=bcc>{{cite journal|doi=10.1103/PhysRevB.84.113104|title=First-principles calculation of the structural stability of 6d transition metals|year=2011|last1=Östlin|first1=A.|last2=Vitos|first2=L.|journal=Physical Review B|volume=84|issue=11|page=113104 |bibcode=2011PhRvB..84k3104O }}</ref>

The table below is a summary of the key physical properties of the group 5 elements. The question-marked value is predicted.<ref name=Haire/>

{| class="wikitable centered plainrowheaders" style="text-align:center;"
|+Properties of the group 5 elements | Properties of the group 5 elements
! scope="col" | Name
! scope="col" | V, [[vanadium]]
! scope="col" | Nb, [[niobium]]
! scope="col" | Ta, [[tantalum]]
! scope="col" | Db, [[dubnium]]
|-
! scope="row" |[[Melting point]]
| 2183 K (1910&nbsp;°C) || 2750 K (2477&nbsp;°C) || 3290 K (3017&nbsp;°C) || {{Unknown}}
|-
! scope="row" |[[Boiling point]]
| 3680 K (3407&nbsp;°C) || 5017 K (4744&nbsp;°C) || 5731 K (5458&nbsp;°C) || {{Unknown}}
|-
! scope="row" |[[Density]]
| 6.11&nbsp;g·cm<sup>−3</sup> || 8.57&nbsp;g·cm<sup>−3</sup> || 16.69&nbsp;g·cm<sup>−3</sup> || 21.6&nbsp;g·cm<sup>−3</sup>?<ref name=density>{{cite journal |last1=Gyanchandani |first1=Jyoti |last2=Sikka |first2=S. K. |title=Physical properties of the 6 d -series elements from density functional theory: Close similarity to lighter transition metals |journal=Physical Review B |date=10 May 2011 |volume=83 |issue=17 |pages=172101 |doi=10.1103/PhysRevB.83.172101|bibcode=2011PhRvB..83q2101G }}</ref><ref name=kratz>{{cite book |last1=Kratz |last2=Lieser |title=Nuclear and Radiochemistry: Fundamentals and Applications |date=2013 |page=631 |edition=3rd}}</ref>
|-
! scope="row" |Appearance
| blue-silver-gray metal || grayish metallic, blue when oxidized ||  gray blue || {{Unknown}}
|-
! scope="row" |[[Atomic radius]]
|  135 pm || 146 pm || 146 pm || 139 pm
|}

=== Vanadium ===

Vanadium is an average-hard, [[ductility|ductile]], steel-blue metal. It is electrically [[conductive]] and thermally [[thermal insulation|insulating]]. Some sources describe vanadium as "soft", perhaps because it is ductile, [[malleable]], and not [[brittle]].<ref>{{cite book|author=George F. Vander Voort|title=Metallography, principles and practice|url=https://books.google.com/books?id=GRQC8zYqtBIC&pg=PA137|access-date=17 September 2011|date=1984|publisher=ASM International|isbn=978-0-87170-672-0|pages=137–}}</ref><ref>{{cite book|last=Cardarelli|first=François|title=Materials handbook: a concise desktop reference|url=https://books.google.com/books?id=PvU-qbQJq7IC&pg=PA338|access-date=17 September 2011|date=2008|publisher=Springer|isbn=978-1-84628-668-1|pages=338–}}</ref> Vanadium is harder than most metals and steels (see [[Hardnesses of the elements (data page)]] and [[iron#Mechanical properties|iron]]). It has good resistance to [[corrosion]] and it is stable against [[alkali]]s and [[sulfuric acid|sulfuric]] and [[hydrochloric acid]]s.<ref name="HollemanAF">{{cite book|publisher= Walter de Gruyter|date= 1985|edition= 91–100|pages= 1071–1075|isbn= 978-3-11-007511-3|title= Lehrbuch der Anorganischen Chemie|first= Arnold F.|last= Holleman|author2= Wiberg, Egon|author3= Wiberg, Nils|chapter= Vanadium |language= de}}</ref> It is [[oxidation|oxidized]] in air at about 933&nbsp;[[Kelvin|K]] (660&nbsp;°C, 1220&nbsp;°F), although an oxide [[passivation (chemistry)|passivation]] layer forms even at room temperature.<ref>{{Cite journal |last=Klinser |first=Gregor |last2=Zettl |first2=Roman |last3=Wilkening |first3=Martin |last4=Krenn |first4=Heinz |last5=Hanzu |first5=Ilie |last6=Würschum |first6=Roland |date=2019 |title=Redox processes in sodium vanadium phosphate cathodes – insights from operando magnetometry |url=https://xlink.rsc.org/?DOI=C9CP04045E |journal=Physical Chemistry Chemical Physics |language=en |volume=21 |issue=36 |pages=20151–20155 |doi=10.1039/C9CP04045E |issn=1463-9076|doi-access=free }}</ref>

=== Niobium ===

Niobium is a [[lustre (mineralogy)|lustrous]], grey, [[ductility|ductile]], [[paramagnetism|paramagnetic]] [[metal]] in group 5 of the [[periodic table]] (see table), with an electron configuration in the outermost [[electron shell|shells]] atypical for group 5. Similarly atypical configurations occur in the neighborhood of [[ruthenium]] (44) and [[rhodium]] (45).<ref>{{Cite journal |last=Scerri |first=Eric R. |date=April 2019 |title=Five ideas in chemical education that must die |url=http://link.springer.com/10.1007/s10698-018-09327-y |journal=Foundations of Chemistry |language=en |volume=21 |issue=1 |pages=61–69 |doi=10.1007/s10698-018-09327-y |issn=1386-4238|url-access=subscription }}</ref>

Although it is thought to have a [[body-centered cubic]] crystal structure from absolute zero to its melting point, high-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies which are inconsistent with a cubic structure.<ref>{{cite journal |last1=Bollinger |first1=R. K. |last2=White |first2=B. D. |last3=Neumeier |first3=J. J. |last4=Sandim |first4=H. R. Z. |last5=Suzuki |first5=Y. |last6=dos Santos |first6=C. A. M. |last7=Avci |first7=R. |last8=Migliori |first8=A. |last9=Betts |first9=J. B. |date=2011 |title=Observation of a Martensitic Structural Distortion in V, Nb, and Ta |journal=Physical Review Letters |volume=107 |issue=7 |pages=075503 |doi=10.1103/PhysRevLett.107.075503 |bibcode=2011PhRvL.107g5503B |pmid=21902404|doi-access=free }}</ref> <!-- Therefore, further research and discovery in this area is expected. -->

Niobium becomes a [[superconductor]] at [[cryogenics|cryogenic]] temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2&nbsp;[[Kelvin|K]].<ref name="Pein">{{cite journal|title = A Superconducting Nb<sub>3</sub>Sn Coated Multicell Accelerating Cavity|first = M.|last = Peiniger|author2=Piel, H. |journal = IEEE Transactions on Nuclear Science|date= 1985|volume= 32|issue = 5|doi = 10.1109/TNS.1985.4334443|pages = 3610–3612|bibcode = 1985ITNS...32.3610P |s2cid = 23988671}}</ref> Niobium has the greatest [[superconductor#Meissner effect|magnetic penetration depth]] of any element.<ref name="Pein" /> In addition, it is one of the three elemental [[Type II superconductor]]s, along with [[vanadium]] and [[technetium]]. The superconductive properties are strongly dependent on the purity of the niobium metal.<ref name="Moura">{{cite journal|title=Melting And Purification of Niobium|first=Hernane R.|last = Salles Moura|author2=Louremjo de Moura, Louremjo |journal=AIP Conference Proceedings|volume=927|date=2007|issue=927|pages=165–178|doi=10.1063/1.2770689|bibcode=2007AIPC..927..165M}}</ref>

When very pure, it is comparatively soft and ductile, but impurities make it harder.<ref name="Nowak">{{cite journal|title=Niobium Compounds: Preparation, Characterization, and Application in Heterogeneous Catalysis|author=Nowak, Izabela|author2=Ziolek, Maria|journal=Chemical Reviews|date=1999|volume=99|issue=12|pages=3603–3624|doi=10.1021/cr9800208|pmid=11849031}}</ref><!--awkward; this either contains redundancy or is leaving something out-->

The metal has a low [[Neutron capture#Capture cross section|capture cross-section]] for thermal [[neutron]]s;<ref>{{cite journal|title = Columbium Alloys Today|author=Jahnke, L. P.|author2=Frank, R. G.|author3=Redden, T. K.|date = 1960|journal = Metal Progr.|volume = 77|issue = 6|pages = 69–74|osti = 4183692}}</ref> thus it is used in the nuclear industries where neutron transparent structures are desired.<ref>{{cite journal|first = A. V.|last = Nikulina|title = Zirconium-Niobium Alloys for Core Elements of Pressurized Water Reactors|journal = Metal Science and Heat Treatment|volume = 45|issue = 7–8|date = 2003|doi = 10.1023/A:1027388503837|pages = 287–292|bibcode = 2003MSHT...45..287N|s2cid = 134841512}}</ref>

=== 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>

=== Dubnium ===

[[File:7s electrons dubnium relativistic vs nonrelativistic.svg|thumb|Relativistic (solid line) and nonrelativistic (dashed line) radial distribution of the 7s valence electrons in dubnium.]]
A direct relativistic effect is that as the atomic numbers of elements increase, the innermost electrons begin to revolve faster around the nucleus as a result of an increase of [[electromagnetic attraction]] between an electron and a nucleus. Similar effects have been found for the outermost s [[Atomic orbital|orbitals]] (and p<sub>1/2</sub> ones, though in dubnium they are not occupied): for example, the 7s orbital contracts by 25% in size and is stabilized by 2.6&nbsp;[[electronvolt|eV]].<ref name="Haire" />

A more indirect effect is that the contracted s and p<sub>1/2</sub> orbitals [[shielding effect|shield]] the charge of the nucleus more effectively, leaving less for the outer d and f electrons, which therefore move in larger orbitals. Dubnium is greatly affected by this: unlike the previous group 5 members, its 7s electrons are slightly more difficult to extract than its 6d electrons.<ref name="Haire" />

[[File:Atomic orbitals dubnium.svg|thumb|Relativistic stabilization of the ''n''s orbitals, the destabilization of the {{nobreak|(''n''-1)d}} orbitals and their spin–orbit splitting for the group 5 elements.]]
Another effect is the [[spin–orbit interaction]], particularly spin–orbit splitting, which splits the 6d subshell—the [[azimuthal quantum number]] ℓ of a d&nbsp;shell is 2—into two subshells, with four of the ten orbitals having their ℓ lowered to 3/2 and six raised to 5/2. All ten energy levels are raised; four of them are lower than the other six. (The three 6d electrons normally occupy the lowest energy levels, 6d<sub>3/2</sub>.)<ref name="Haire" />

A single ionized atom of dubnium (Db<sup>+</sup>) should lose a 6d electron compared to a neutral atom; the doubly (Db<sup>2+</sup>) or triply (Db<sup>3+</sup>) ionized atoms of dubnium should eliminate 7s electrons, unlike its lighter homologs. Despite the changes, dubnium is still expected to have five valence electrons; 7p energy levels have not been shown to influence dubnium and its properties. As the 6d orbitals of dubnium are more destabilized than the 5d ones of tantalum, and Db<sup>3+</sup> is expected to have two 6d, rather than 7s, electrons remaining, the resulting +3 oxidation state is expected to be unstable and even rarer than that of tantalum. The ionization potential of dubnium in its maximum +5 oxidation state should be slightly lower than that of tantalum and the ionic radius of dubnium should increase compared to tantalum; this has a significant effect on dubnium's chemistry.<ref name=Haire>{{cite book| title=The Chemistry of the Actinide and Transactinide Elements| editor1-last=Morss|editor1-first=L.R.|editor2-first=N. M.| editor2-last=Edelstein| editor3-last=Fuger|editor3-first=Jean| last1=Hoffman|first1=D. C. |last2=Lee |first2=D. M. |last3=Pershina |first3=V.|chapter=Transactinides and the future elements| publisher= [[Springer Science+Business Media]]| year=2006| isbn=978-1-4020-3555-5| edition=3rd|pages=1652–1752| ref=CITEREFHaire2006}}</ref>

Atoms of dubnium in the solid state should arrange themselves in a [[body-centered cubic]] configuration, like the previous group 5 elements.<ref name="bcc" /> The predicted density of dubnium is 21.6&nbsp;g/cm<sup>3</sup>.<ref name="density" />