:Group 5 element

File:'Andrés Manuel de Río' (1825) by Rafael Ximeno y Planes - Museo Tolsá - Palacio de Minería - Mexico 2024.jpg

Group 5 is the new IUPAC name for this group; the old style name was group VB in the old US system (CAS) or group VA in the European system (old IUPAC). Group 5 must not be confused with the group with the old-style group crossed names of either VA (US system, CAS) or VB (European system, old IUPAC); that group is now called the pnictogens or group 15.{{cite journal |last1=Fluck |first1=E. |year=1988 |title=New Notations in the Periodic Table |url=http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |journal=Pure Appl. Chem. |publisher=IUPAC |volume=60 |issue=3 |pages=431–436 |doi=10.1351/pac198860030431 |s2cid=96704008 |access-date=24 March 2012}}

Vanadium was discovered in 1801 by the Spanish mineralogist Andrés Manuel del Río. Del Río extracted the element from a sample of Mexican "brown lead" ore, later named vanadinite. He found that its salts exhibit a wide variety of colors, and as a result he named the element panchromium (Greek: παγχρώμιο "all colors"). Later, Del Río renamed the element erythronium (Greek: ερυθρός "red") because most of the salts turned red upon heating. In 1805, French chemist Hippolyte Victor Collet-Descotils, backed by del Río's friend Baron Alexander von Humboldt, incorrectly declared that del Río's new element was an impure sample of chromium. Del Río accepted Collet-Descotils' statement and retracted his claim.{{cite journal|title= The Road to Chemical Names and Eponyms: Discovery, Priority, and Credit|author= Cintas, Pedro|journal= Angewandte Chemie International Edition|volume= 43|issue= 44|date= 2004|pmid= 15376297|doi= 10.1002/anie.200330074|pages= 5888–94}}

In 1831 Swedish chemist Nils Gabriel Sefström rediscovered the element in a new oxide he found while working with iron ores. Later that year, Friedrich Wöhler confirmed del Río's earlier work.{{cite journal|title= Ueber das Vanadin, ein neues Metall, gefunden im Stangeneisen von Eckersholm, einer Eisenhütte, die ihr Erz von Taberg in Småland bezieht|first= N. G.|last= Sefström|journal= Annalen der Physik und Chemie|volume= 97|issue= 1|pages= 43–49|date= 1831|doi= 10.1002/andp.18310970103|bibcode= 1831AnP....97...43S|url= https://zenodo.org/record/1423544}} Sefström chose a name beginning with V, which had not yet been assigned to any element. He called the element vanadium after Old Norse Vanadís (another name for the Norse Vanir goddess Freyja, whose attributes include beauty and fertility), because of the many beautifully colored chemical compounds it produces. In 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed rionium after del Río, but this suggestion was not followed.{{cite journal |journal= The Monthly American Journal of Geology and Natural Science |first= George William|last= Featherstonhaugh |title=New Metal, provisionally called Vanadium |year= 1831|page=69 |url= https://archive.org/stream/monthlyamericanj11831phil#page/68/mode/2up/search/rionium}}

File:Charles Hatchett. Soft-ground etching by F. C. Lewis after T Wellcome V0002614 (cropped).jpg

Niobium was identified by English chemist Charles Hatchett in 1801.{{cite journal|last=Hatchett|first=Charles|author-link=Charles Hatchett|year=1802|url=https://books.google.com/books?id=c-Q_AAAAYAAJ&pg=PA49|title=An analysis of a mineral substance from North America, containing a metal hitherto unknown|journal=Philosophical Transactions of the Royal Society of London|volume=92|pages=49–66|jstor=107114|doi=10.1098/rspl.1800.0045|doi-access=free|access-date=15 July 2016|archive-date=3 May 2016|archive-url=https://web.archive.org/web/20160503233004/https://books.google.com/books?id=c-Q_AAAAYAAJ&pg=PA49|url-status=live}}{{Citation |last=Hatchett |first=Charles |author-link=Charles Hatchett |year=1802 |title=Outline of the Properties and Habitudes of the Metallic Substance, lately discovered by Charles Hatchett, Esq. and by him denominated Columbium |journal=Journal of Natural Philosophy, Chemistry, and the Arts |volume=I (January) |pages=32–34 |url=https://books.google.com/books?id=ylZwOmyBA7IC&pg=PA32 |postscript=. |access-date=13 July 2017 |archive-date=24 December 2019 |archive-url=https://web.archive.org/web/20191224164852/https://books.google.com/books?id=ylZwOmyBA7IC&pg=PA32 |url-status=live }}{{cite journal |last=Hatchett |first=Charles |author-link=Charles Hatchett |year=1802 |title=Eigenschaften und chemisches Verhalten des von Charles Hatchett entdeckten neuen Metalls, Columbium |trans-title=Properties and chemical behavior of the new metal, columbium, (that was) discovered by Charles Hatchett |language=de |journal=Annalen der Physik |volume=11 |issue=5 |pages=120–122 |url=https://books.google.com/books?id=wSYwAAAAYAAJ&pg=PA120 |doi=10.1002/andp.18020110507 |bibcode=1802AnP....11..120H |access-date=15 July 2016 |archive-date=9 May 2016 |archive-url=https://web.archive.org/web/20160509100435/https://books.google.com/books?id=wSYwAAAAYAAJ&pg=PA120 |url-status=live }} He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral columbite and the new element columbium after Columbia,{{cite journal|title = Reaction of Tantalum, Columbium and Vanadium with Iodine|first = F.|last = Kòrösy|journal = Journal of the American Chemical Society|date = 1939|volume = 61|issue = 4|pages = 838–843|doi = 10.1021/ja01873a018}} the poetic name for the United States.{{cite journal|last=Percival|first=James|title=Middletown Silver and Lead Mines|journal=Journal of Silver and Lead Mining Operations|date=January 1853|volume=1|page=186|url=https://play.google.com/store/books/details?id=MFILAAAAYAAJ&rdid=book-MFILAAAAYAAJ&rdot=1|access-date=24 April 2013|archive-date=3 June 2013|archive-url=https://web.archive.org/web/20130603002528/https://play.google.com/store/books/details?id=MFILAAAAYAAJ&rdid=book-MFILAAAAYAAJ&rdot=1|url-status=live}}{{cite journal|title = Charles Hatchett FRS (1765–1847), Chemist and Discoverer of Niobium|first = William P.|last = Griffith|author2=Morris, Peter J. T. |journal = Notes and Records of the Royal Society of London|volume = 57|issue = 3|pages = 299–316|date = 2003|jstor = 3557720|doi = 10.1098/rsnr.2003.0216|s2cid = 144857368}} However, after the 15th Conference of the Union of Chemistry in Amsterdam in 1949, the name niobium was chosen for element 41.{{cite journal |first = Geoff|last = Rayner-Canham|author2=Zheng, Zheng |title = Naming elements after scientists: an account of a controversy|journal = Foundations of Chemistry|volume = 10|issue = 1|date = 2008|doi = 10.1007/s10698-007-9042-1|pages = 13–18|s2cid = 96082444}} The columbium discovered by Hatchett was probably a mixture of the new element with tantalum, which was first discovered in 1802 by Anders Gustav Ekeberg.{{cite book| last = Noyes| first = William Albert| title = A Textbook of Chemistry| publisher = H. Holt & Co.| page = 523| url = https://books.google.com/books?id=UupHAAAAIAAJ&q=columbium+discovered+by+Hatchett+was+a+mixture+of+two+elements&pg=PA523| date = 1918| access-date = 2 November 2020| archive-date = 2 June 2022| archive-url = https://web.archive.org/web/20220602091834/https://books.google.com/books?id=UupHAAAAIAAJ&q=columbium+discovered+by+Hatchett+was+a+mixture+of+two+elements&pg=PA523| url-status = live}}

File:Anders Gustaf Ekeberg.jpg

Subsequently, there was considerable confusion{{cite journal|title = On the Identity of Columbium and Tantalum|pages = 246–252|journal = Philosophical Transactions of the Royal Society|first = William Hyde|last = Wollaston|author-link = William Hyde Wollaston|doi = 10.1098/rstl.1809.0017| jstor = 107264|volume = 99|date = 1809|s2cid = 110567235}} over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm{{sup|3}}, and tantalum—tantalite, with a density over 8 g/cm{{sup|3}}, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum. This conclusion was disputed in 1846 by German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: niobium (from Niobe) and pelopium (from Pelops).{{cite journal|title = Ueber die Zusammensetzung der Tantalite und ein im Tantalite von Baiern enthaltenes neues Metall|pages = 317–341|journal = Annalen der Physik|author-link = Heinrich Rose|language = de|first = Heinrich|last = Rose|doi = 10.1002/andp.18441391006|url = http://gallica.bnf.fr/ark:/12148/bpt6k15148n/f327.table|volume = 139|issue = 10|date = 1844|bibcode = 1844AnP...139..317R|access-date = 31 August 2008|archive-date = 20 June 2013|archive-url = https://web.archive.org/web/20130620093605/http://gallica.bnf.fr/ark:/12148/bpt6k15148n/f327.table|url-status = live}}{{cite journal|title = Ueber die Säure im Columbit von Nordamérika|language = de|pages = 572–577|first = Heinrich|last = Rose|journal = Annalen der Physik|doi = 10.1002/andp.18471460410|url = http://gallica.bnf.fr/ark:/12148/bpt6k15155x/f586.table|date = 1847|volume = 146|issue = 4|author-link = Heinrich Rose|bibcode = 1847AnP...146..572R|access-date = 31 August 2008|archive-date = 11 May 2014|archive-url = https://web.archive.org/web/20140511114909/http://gallica.bnf.fr/ark:/12148/bpt6k15155x/f586.table|url-status = live}} This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium, and dianium{{cite journal|title = Ueber eine eigenthümliche Säure, Diansäure, in der Gruppe der Tantal- und Niob- verbindungen|first = V.|last = Kobell|journal = Journal für Praktische Chemie|volume = 79|issue = 1|pages = 291–303|doi = 10.1002/prac.18600790145|date = 1860|url = https://zenodo.org/record/1427822|access-date = 5 October 2019|archive-date = 5 October 2019|archive-url = https://web.archive.org/web/20191005220552/https://zenodo.org/record/1427822|url-status = live}} were in fact identical to niobium or mixtures of niobium and tantalum.{{cite journal|title = Tantalsäure, Niobsäure, (Ilmensäure) und Titansäure|journal = Fresenius' Journal of Analytical Chemistry|volume = 5|issue = 1|date = 1866|doi = 10.1007/BF01302537|pages = 384–389|author= Marignac, Blomstrand|author2= Deville, H. |author3= Troost, L. |author4= Hermann, R. |s2cid = 97246260}} Pure tantalum was not produced until 1903.

The last element of the group, dubnium, does not occur naturally and so must be synthesized in a laboratory. The first reported detection was by a team at the Joint Institute for Nuclear Research (JINR), which in 1968 had produced the new element by bombarding an americium-243 target with a beam of neon-22 ions, and reported 9.4 MeV (with a half-life of 0.1–3 seconds) and 9.7 MeV (t_1/2 > 0.05 s) alpha activities followed by alpha activities similar to those of either ²⁵⁶103 or ²⁵⁷103. Based on prior theoretical predictions, the two activity lines were assigned to ²⁶¹105 and ²⁶⁰105, respectively.{{Cite journal|year=1993|title=Discovery of the Transfermium elements|url=http://s3.documentcloud.org/documents/562229/iupac1.pdf|journal=Pure and Applied Chemistry|volume=65|issue=8|pages=1757|doi=10.1351/pac199365081757|access-date=September 7, 2016|last1=Barber|first1=R. C.|last2=Greenwood|first2=N. N.|author-link2=Norman Greenwood|last3=Hrynkiewicz|first3=A. Z.|display-authors=3|last4=Jeannin|first4=Y. P|last5=Lefort|first5=M|last6=Sakai|first6=M|last7=Ulehla|first7=I|last8=Wapstra|first8=A. H|last9=Wilkinson|first9=D. H|s2cid=195819585}}

After observing the alpha decays of element 105, the researchers aimed to observe the spontaneous fission (SF) of the element and study the resulting fission fragments. They published a paper in February 1970, reporting multiple examples of two such activities, with half-lives of 14 ms and {{val|2.2|0.5|u=s}}. They assigned the former activity to ^242mfAm{{efn|This notation signifies that the nucleus is a nuclear isomer that decays via spontaneous fission.}} and ascribed the latter activity to an isotope of element 105. They suggested that it was unlikely that this activity could come from a transfer reaction instead of element 105, because the yield ratio for this reaction was significantly lower than that of the ^242mfAm-producing transfer reaction, in accordance with theoretical predictions. To establish that this activity was not from a (²²Ne,xn) reaction, the researchers bombarded a ²⁴³Am target with ¹⁸O ions; reactions producing ²⁵⁶103 and ²⁵⁷103 showed very little SF activity (matching the established data), and the reaction producing heavier ²⁵⁸103 and ²⁵⁹103 produced no SF activity at all, in line with theoretical data. The researchers concluded that the activities observed came from SF of element 105.

JINR then attempted an experiment to create element 105, published in a report in May 1970. They claimed that they had synthesized more nuclei of element 105 and that the experiment confirmed their previous work. According to the paper, the isotope produced by JINR was probably ²⁶¹105, or possibly ²⁶⁰105. This report included an initial chemical examination: the thermal gradient version of the gas-chromatography method was applied to demonstrate that the chloride of what had formed from the SF activity nearly matched that of niobium pentachloride, rather than hafnium tetrachloride. The team identified a 2.2-second SF activity in a volatile chloride portraying eka-tantalum properties, and inferred that the source of the SF activity must have been element 105.

In June 1970, JINR made improvements on their first experiment, using a purer target and reducing the intensity of transfer reactions by installing a collimator before the catcher. This time, they were able to find 9.1 MeV alpha activities with daughter isotopes identifiable as either ²⁵⁶103 or ²⁵⁷103, implying that the original isotope was either ²⁶⁰105 or ²⁶¹105.

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A controversy erupted on who had discovered the element, which each group suggesting its own name: the Dubna group named the element nielsbohrium after Niels Bohr, while the Berkeley group named it hahnium after Otto Hahn.{{cite book |last1=Hoffman |first1=D. C. |last2=Ghiorso |first2=A. |last3=Seaborg |first3=G. T. |title=The Transuranium People: The Inside Story |year=2000 |pages=369–399 |publisher=Imperial College Press |isbn=978-1-86094-087-3}} Eventually a joint working party of IUPAC and IUPAP, the Transfermium Working Group, decided that credit for the discovery should be shared. After various compromises were attempted, where element 105 was called kurchatovium, joliotium and hahnium, in 1997 IUPAC officially named the element dubnium after Dubna,{{cite journal |doi =10.1351/pac199769122471 |title =Names and symbols of transfermium elements (IUPAC Recommendations 1997) |date =1997 |journal =Pure and Applied Chemistry |volume =69 |issue = 12 |pages =2471–2474|doi-access =free }} and nielsbohrium was eventually simplified to bohrium and used for element 107.{{cite journal |last1=Ghiorso |first1=A. |last2=Seaborg |first2=G. T. |last3=Organessian |first3=Yu. Ts. |last4=Zvara |first4=I. |last5=Armbruster |first5=P. |last6=Hessberger |first6=F. P. |last7=Hofmann |first7=S. |last8=Leino |first8=M. |last9=Munzenberg |first9=G. |last10=Reisdorf |first10=W. |last11=Schmidt |first11=K.-H. |year=1993 |title=Responses on 'Discovery of the transfermium elements' by Lawrence Berkeley Laboratory, California; Joint Institute for Nuclear Research, Dubna; and Gesellschaft fur Schwerionenforschung, Darmstadt followed by reply to responses by the Transfermium Working Group |journal=Pure and Applied Chemistry |volume=65 |issue=8 |pages=1815–1824 |doi=10.1351/pac199365081815 |doi-access=free}}{{Cite journal |author=Commission on Nomenclature of Inorganic Chemistry |date=1997 |title=Names and symbols of transfermium elements (IUPAC Recommendations 1997) |url=http://publications.iupac.org/pac/pdf/1997/pdf/6912x2471.pdf |url-status=live |journal=Pure and Applied Chemistry |volume=69 |issue=12 |pages=2471–2474 |doi=10.1351/pac199769122471 |archive-url=https://web.archive.org/web/20211011132719/http://publications.iupac.org/pac/pdf/1997/pdf/6912x2471.pdf |archive-date=2021-10-11 |access-date=2023-07-11}}

Like other groups, the members of this family show patterns in its electron configuration, especially the outermost shells. (The expected 4d³ 5s² configuration for niobium is a very low-lying excited state at about 0.14 eV.)[https://physics.nist.gov/PhysRefData/ASD/levels_form.html NIST Atomic Spectra Database]

Most of the chemistry has been observed only for the first three members of the group (the chemistry of dubnium is not very established, but what is known appears to match expectations for a heavier congener of tantalum). All the elements of the group are reactive metals with a high melting points (1910 °C, 2477 °C, 3017 °C). The reactivity is not always obvious due to the rapid formation of a stable oxide layer, which prevents further reactions, similarly to trends in group 3 or group 4. The metals form different oxides: vanadium forms vanadium(II) oxide, vanadium(III) oxide, vanadium(IV) oxide and vanadium(V) oxide, niobium forms niobium(II) oxide, niobium(IV) oxide and niobium(V) oxide, but out of tantalum oxides only tantalum(V) oxide is characterized. Metal(V) oxides are generally nonreactive and act like acids rather than bases, but the lower oxides are less stable. They, however, have some unusual properties for oxides, such as high electric conductivity.

All three elements form various inorganic compounds, generally in the oxidation state of +5. Lower oxidation states are also known, but in all elements other than vanadium,{{cite book |last=Holleman |first=Arnold F. |title=Lehrbuch der Anorganischen Chemie |author2=Wiberg, Egon |author3=Wiberg, Nils |date=1985 |publisher=Walter de Gruyter |isbn=978-3-11-007511-3 |edition=91–100 |pages=1071–1075 |language=de |chapter=Vanadium}} they are less stable, decreasing in stability with atomic mass increase.

Vanadium forms oxides in the +2, +3, +4 and +5 oxidation states, forming vanadium(II) oxide (VO), vanadium(III) oxide (V₂O₃), vanadium(IV) oxide (VO₂) and vanadium(V) oxide (V₂O₅). 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.{{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}}

Niobium forms oxides in the oxidation states +5 (Niobium pentoxide),{{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}} +4 (Niobium dioxide), and the rarer oxidation state, +2 (NbO). Most common is the pentoxide, also being precursor to almost all niobium compounds and alloys.{{cite book|first = Francois|last = Cardarelli|date = 2008|title = Materials Handbook |publisher = Springer London|isbn = 978-1-84628-668-1}}

Tantalum pentoxide (Ta₂O₅) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including many defect structures, and are lightly studied or poorly characterized.{{Greenwood&Earnshaw2nd}}

File:decavanadate polyhedra.png structure]]

In aqueous solution, vanadium(V) forms an extensive family of oxyanions as established by ⁵¹V NMR spectroscopy.{{cite book |doi=10.1016/S0066-4103(07)62002-X|title=Vanadium-51 NMR|series=Annual Reports on NMR Spectroscopy|year=2007|last1=Rehder|first1=D.|last2=Polenova|first2=T.|last3=Bühl|first3=M.|volume=62|pages=49–114|isbn=9780123739193}} The interrelationships in this family are described by the predominance diagram, which shows at least 11 species, depending on pH and concentration.{{Greenwood&Earnshaw|page=984}} The tetrahedral orthovanadate ion, {{chem|VO|4|3−}}, is the principal species present at pH 12–14. Similar in size and charge to phosphorus(V), vanadium(V) also parallels its chemistry and crystallography. Orthovanadate V{{chem|O|4|3−}} is used in protein crystallography{{cite journal|volume= 577|issue= 3|doi= 10.1016/j.febslet.2004.10.022|pmid= 15556602|date= 2004|title= The power of vanadate in crystallographic investigations of phosphoryl transfer enzymes|first1= Irmgard|last1= Sinning|journal= FEBS Letters|last2= Hol|first2= Wim G. J.|pages= 315–21|s2cid= 8328704|doi-access= free|bibcode= 2004FEBSL.577..315D}} to study the biochemistry of phosphate.{{cite journal|volume= 181|pmc= 1161148|date= 1979|title= Inhibition of human alkaline phosphatases by vanadate|first= Lorne E.|last= Seargeant|author2=Stinson, Robert A. |journal= Biochemical Journal|pmid=486156|issue=1|pages= 247–50|doi= 10.1042/bj1810247}} Beside that, this anion also has been shown to interact with activity of some specific enzymes.{{Cite journal |last1=Crans |first1=Debbie C. |last2=Simone |first2=Carmen M. |date=1991-07-09 |title=Nonreductive interaction of vanadate with an enzyme containing a thiol group in the active site: glycerol-3-phosphate dehydrogenase |url=https://pubs.acs.org/doi/abs/10.1021/bi00241a015 |journal=Biochemistry |language=en |volume=30 |issue=27 |pages=6734–6741 |doi=10.1021/bi00241a015 |pmid=2065057 |issn=0006-2960}}{{Cite journal |last1=Karlish |first1=S. J. D. |last2=Beaugé |first2=L. A. |last3=Glynn |first3=I. M. |date=Nov 1979 |title=Vanadate inhibits (Na+ + K+)ATPase by blocking a conformational change of the unphosphorylated form |url=https://www.nature.com/articles/282333a0 |journal=Nature |language=en |volume=282 |issue=5736 |pages=333–335 |doi=10.1038/282333a0 |pmid=228199 |bibcode=1979Natur.282..333K |s2cid=4341480 |issn=1476-4687}} The tetrathiovanadate [VS₄]³⁻ is analogous to the orthovanadate ion.{{Greenwood&Earnshaw|page=988}}

At lower pH values, the monomer [HVO₄]²⁻ and dimer [V₂O₇]⁴⁻ are formed, with the monomer predominant at vanadium concentration of less than c. 10⁻²M (pV > 2, where pV is equal to the minus value of the logarithm of the total vanadium concentration/M). The formation of the divanadate ion is analogous to the formation of the dichromate ion. As the pH is reduced, further protonation and condensation to polyvanadates occur: at pH 4–6 [H₂VO₄]⁻ is predominant at pV greater than ca. 4, while at higher concentrations trimers and tetramers are formed. Between pH 2–4 decavanadate predominates, though its formation from orthovanadate is optimized at pH 4–7, represented by this reaction:{{cite book |author1=Johnson, G. |title=Inorganic Syntheses |author2=Murmann, R. K. |date=1979 |isbn=978-0-471-04542-7 |volume=19 |pages=140–145 |chapter=Sodium and Ammonium Decayanadates(V) |doi=10.1002/9780470132500.ch32}}

:{{Chem2|10 Na3[VO4] + 24 HOAc → Na6[V10O28] + 12 H2O + 24 NaOAc}}

In decavanadate, each V(V) center is surrounded by six oxide ligands. Vanadic acid, H₃VO₄ exists only at very low concentrations because protonation of the tetrahedral species [H₂VO₄]⁻ results in the preferential formation of the octahedral [VO₂(H₂O)₄]⁺ species. In strongly acidic solutions, pH < 2, [VO₂(H₂O)₄]⁺ is the predominant species, while the oxide V₂O₅ precipitates from solution at high concentrations.{{Cite journal |last=Sadoc |first=Aymeric |last2=Messaoudi |first2=Sabri |last3=Furet |first3=Eric |last4=Gautier |first4=Régis |last5=Le Fur |first5=Eric |last6=le Pollès |first6=Laurent |last7=Pivan |first7=Jean-Yves |date=2007-06-01 |title=Structure and Stability of VO 2 + in Aqueous Solution: A Car−Parrinello and Static ab Initio Study |url=https://pubs.acs.org/doi/10.1021/ic0614519 |journal=Inorganic Chemistry |language=en |volume=46 |issue=12 |pages=4835–4843 |doi=10.1021/ic0614519 |issn=0020-1669}} The oxide is formally the acid anhydride of vanadic acid. The structures of many vanadate compounds have been determined by X-ray crystallography.{{Cite journal |last=Davies |first=Douglas R. |last2=Hol |first2=Wim G.J. |date=2004-11-19 |title=The power of vanadate in crystallographic investigations of phosphoryl transfer enzymes |url=https://febs.onlinelibrary.wiley.com/doi/10.1016/j.febslet.2004.10.022 |journal=FEBS Letters |language=en |volume=577 |issue=3 |pages=315–321 |doi=10.1016/j.febslet.2004.10.022 |issn=0014-5793}}

File:VinwaterPourbaixdiagram2.svg for vanadium in water, which shows the redox potentials between various vanadium species in different oxidation states.{{cite journal|journal= Electrochimica Acta|volume= 42|date= 1997|pages= 579–586|doi= 10.1016/S0013-4686(96)00202-2|title= Electrochemical behavior of vanadium in aqueous solutions of different pH|first= F. M.|last= Al-Kharafi|author2=Badawy, W. A. |issue= 4}}]]

Vanadium(V) forms various peroxo complexes, most notably in the active site of the vanadium-containing bromoperoxidase enzymes. The species VO(O)₂(H₂O)₄⁺ is stable in acidic solutions. In alkaline solutions, species with 2, 3 and 4 peroxide groups are known; the last forms violet salts with the formula M₃V(O₂)₄ nH₂O (M= Li, Na, etc.), in which the vanadium has an 8-coordinate dodecahedral structure.{{Greenwood&Earnshaw}}, p994.{{cite book|date=1992|url=https://books.google.com/books?id=Lmt3x9CyfLgC&pg=PA128|page=128|title=Catalytic oxidations with hydrogen peroxide as oxidant|author=Strukul, Giorgio|publisher=Springer|isbn=978-0-7923-1771-5}}

Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate ({{chem2|LiNbO3}}) and lanthanum niobate ({{chem2|LaNbO4}}). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone {{chem|NbO|4|3-}} ions.

Tantalates, compounds containing [TaO₄]³⁻ or [TaO₃]⁻ are numerous. Lithium tantalate (LiTaO₃) adopts a perovskite structure. Lanthanum tantalate (LaTaO₄) contains isolated {{chem|TaO|4|3−}} tetrahedra.

Twelve binary halides, compounds with the formula VX_n (n=2...5), are known. VI₄, VCl₅, VBr₅, and VI₅ do not exist or are extremely unstable; the only known pure V{{Sup|5+}} halide compound is {{Chem2|VF5|link=vanadium pentafluoride}}.{{Citation |title=Vanadium series products and functional materials |date=2021 |work=Vanadium |pages=395–413 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780128188989000140 |access-date=2024-11-11 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-818898-9.00014-0 |isbn=978-0-12-818898-9}} In combination with other reagents, VCl₄ is used as a catalyst for polymerization of dienes. Like all binary halides, those of vanadium are Lewis acidic, especially those of V(IV) and V(V). Many of the halides form octahedral complexes with the formula VX_nL_6−n (X= halide; L= other ligand).{{Cite journal |last=VonDreele |first=Robert B. |last2=Fay |first2=Robert C. |date=November 1972 |title=Octahedral vanadium(IV) complexes. Synthesis and stereochemistry of vanadium(IV) .beta.-diketonates |url=https://pubs.acs.org/doi/abs/10.1021/ja00777a052 |journal=Journal of the American Chemical Society |language=en |volume=94 |issue=22 |pages=7935–7936 |doi=10.1021/ja00777a052 |issn=0002-7863}}{{Cite journal |last=Halepoto |first=Dost M |last2=Larkworthy |first2=Leslie F |last3=Povey |first3=David C |last4=Smith |first4=Gallienus W |last5=Ramdas |first5=Vijayalaksmi |date=June 1995 |title=Some complex halides of vanadium(II) and vanadium(III). The crystal and molecular structure of tetrakis(methylammonium) hexachlorovanadate(III) chloride |url=https://linkinghub.elsevier.com/retrieve/pii/0277538794004139 |journal=Polyhedron |language=en |volume=14 |issue=11 |pages=1453–1460 |doi=10.1016/0277-5387(94)00413-9}}

Many vanadium oxyhalides (formula VO_mX_n) are known.{{Greenwood&Earnshaw|page=993}} The oxytrichloride and oxytrifluoride (VOCl₃ and VOF₃) are the most widely studied. Akin to POCl₃, they are volatile, adopt tetrahedral structures in the gas phase, and are Lewis acidic.{{Cite book |url=https://www.degruyter.com/document/doi/10.1515/9783110495904/html |title=Nebengruppenelemente, Lanthanoide, Actinoide, Transactinoide |date=2016-12-19 |publisher=De Gruyter |isbn=978-3-11-049590-4 |editor-last=Holleman |editor-first=Arnold F. |pages=1819-1825 |language=de |chapter=Kapitel XXVI. Die Vanadiumgruppe |doi=10.1515/9783110495904}}

File:Niobium pentachloride solid.jpg

File:Niobium-pentachloride-from-xtal-3D-balls.png, which exists as a dimer]]

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds.{{cite book|first = Anatoly|last = Agulyansky|title = The Chemistry of Tantalum and Niobium Fluoride Compounds|pages = 1–11|publisher = Elsevier|date=2004| isbn = 978-0-444-51604-6}} The pentahalides ({{chem|NbX|5}}) feature octahedral Nb centres. Niobium pentafluoride ({{chem2|NbF5}}) is a white solid with a melting point of 79.0 °C and niobium pentachloride ({{chem2|NbCl5}}) is yellow (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as {{chem2|NbOCl3}}. The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride ({{chem|(C|5|H|5|)|2|NbCl|2}}).{{cite book|author = Lucas, C. R. |author2 = Labinger, J. A. |author3 = Schwartz, J. |title = Inorganic Syntheses |chapter = Dichlorobis(η ⁵ -Cyclopentadienyl) Niobium(IV) |editor1-link=Robert Angelici|editor-first = Robert J.|editor-last = Angelici|date = 1990|volume = 28|pages = 267–270|isbn = 978-0-471-52619-3|doi = 10.1002/9780470132593.ch68|location = New York}} The tetrahalides ({{chem|NbX|4}}) are dark-coloured polymers with Nb-Nb bonds; for example, the black hygroscopic niobium tetrafluoride ({{chem2|NbF4}}){{Cite journal |last=Gortsema |first=F. P. |last2=Didchenko |first2=R. |date=February 1965 |title=The Preparation and Properties of Niobium Tetrafluoride and Oxyfluorides |url=https://pubs.acs.org/doi/abs/10.1021/ic50024a012 |journal=Inorganic Chemistry |language=en |volume=4 |issue=2 |pages=182–186 |doi=10.1021/ic50024a012 |issn=0020-1669}} and dark violet niobium tetrachloride ({{chem2|NbCl4}}).Macintyre, J.E.; Daniel, F.M.; Chapman and Hall; Stirling, V.M. Dictionary of Inorganic Compounds. 1992, Cleveland, OH: CRC Press, p. 2957

Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is [NbF₇]²⁻, an intermediate in the separation of Nb and Ta from the ores.{{cite journal|title = Staff-Industry Collaborative Report: Tantalum and Niobium|author=Soisson, Donald J.|author2=McLafferty, J. J.|author3=Pierret, James A.| journal = Industrial and Engineering Chemistry|date = 1961|volume = 53|issue = 11|pages = 861–868|doi = 10.1021/ie50623a016}} This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral [{{chem2|NbCl6}}]{{sup|−}}:

:{{chem2|Nb2Cl10}} + 2 Cl{{sup|−}} → 2 [{{chem2|NbCl6}}]{{sup|−}}

As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being [{{chem2|Nb6Cl18}}]{{sup|4−}}.

Tantalum halides span the oxidation states of +5, +4, and +3. Tantalum pentafluoride (TaF₅) is a white solid with a melting point of 97.0 °C. The anion [TaF₇]^2- is used for its separation from niobium. The chloride tantalum(V) chloride, 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.

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 metals, though impurities of carbon, nitrogen, and oxygen make them brittle.{{Greenwood&Earnshaw2nd|page=956-958}} They all crystallize in the body-centered cubic structure at room temperature,{{Greenwood&Earnshaw2nd|page=946-948}} and dubnium is expected to do the same.{{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 }}

The table below is a summary of the key physical properties of the group 5 elements. The question-marked value is predicted.

Vanadium is an average-hard, ductile, steel-blue metal. It is electrically conductive and thermally insulating. Some sources describe vanadium as "soft", perhaps because it is ductile, malleable, and not brittle.{{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–}}{{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–}} Vanadium is harder than most metals and steels (see Hardnesses of the elements (data page) and iron). It has good resistance to corrosion and it is stable against alkalis and sulfuric and hydrochloric acids.{{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}} It is oxidized in air at about 933 K (660 °C, 1220 °F), although an oxide passivation layer forms even at room temperature.{{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 }}

Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. Similarly atypical configurations occur in the neighborhood of ruthenium (44) and rhodium (45).{{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}}

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.{{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 }}

Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2 K.{{cite journal|title = A Superconducting Nb₃Sn 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}} Niobium has the greatest magnetic penetration depth of any element. In addition, it is one of the three elemental Type II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal.{{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}}

When very pure, it is comparatively soft and ductile, but impurities make it harder.{{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}}

The metal has a low capture cross-section for thermal neutrons;{{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}} thus it is used in the nuclear industries where neutron transparent structures are desired.{{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}}

Tantalum is dark (blue-gray),{{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 }} dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to corrosion by acids; in fact, at temperatures below 150 °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 °C (boiling point 5458 °C) is exceeded among the elements only by tungsten,{{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}} rhenium{{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=}} osmium,{{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}} and carbon.{{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}}

Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relatively ductile and soft; it has body-centered cubic structure (space group Im3m, lattice constant a = 0.33058 nm), 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 nm, c = 0.5313 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 °C. Bulk tantalum is almost entirely alpha phase, and the beta phase usually exists as thin films{{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}} obtained by magnetron

sputtering, chemical vapor deposition or electrochemical deposition from a eutectic molten salt solution.{{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}}

File:7s electrons dubnium relativistic vs nonrelativistic.svg

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 orbitals (and p_1/2 ones, though in dubnium they are not occupied): for example, the 7s orbital contracts by 25% in size and is stabilized by 2.6 eV.

A more indirect effect is that the contracted s and p_1/2 orbitals 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.

File:Atomic orbitals dubnium.svg

Another effect is the spin–orbit interaction, particularly spin–orbit splitting, which splits the 6d subshell—the azimuthal quantum number ℓ of a d 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_3/2.)

A single ionized atom of dubnium (Db⁺) should lose a 6d electron compared to a neutral atom; the doubly (Db²⁺) or triply (Db³⁺) 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 Db³⁺ 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.{{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}}

Atoms of dubnium in the solid state should arrange themselves in a body-centered cubic configuration, like the previous group 5 elements. The predicted density of dubnium is 21.6 g/cm³.

There are 160 parts per million of vanadium in the Earth's crust, making it the 19th most abundant element. Soil contains on average 100 parts per million of vanadium, and seawater contains 1.5 parts per billion of vanadium. A typical human contains 285 parts per billion of vanadium. Over 60 vanadium ores are known, including vanadinite, patronite, and carnotite.{{cite book|last=Emsley|first=John|title=Nature's Building Blocks|year=2011}} There are 20 parts per million of niobium in the Earth's crust, making it the 33rd most abundant element there. Soil contains on average 24 parts per million of niobium, and seawater contains 900 parts per quadrillion of niobium. A typical human contains 21 parts per billion of niobium. Niobium is in the minerals columbite and pyrochlore. There are 2 parts per million of tantalum in the Earth's crust, making it the 51st most abundant element there. Soil contains on average 1 to 2 parts per billion of tantalum, and seawater contains 2 parts per trillion of tantalum. A typical human contains 2.9 parts per billion of tantalum. Tantalum is found in the minerals tantalite and pyrochlore. Dubnium does not occur naturally in the Earth's crust, as it has no stable isotopes.{{cite book |last1=Münzenberg |first1=G. |title=Handbook of Nuclear Chemistry |last2=Gupta |first2=M. |publisher=Springer |year=2011 |page=877 |chapter=Production and Identification of Transactinide Elements |doi=10.1007/978-1-4419-0720-2_19}}

Vanadium metal is obtained by a multistep process that begins with roasting crushed ore with NaCl or Na₂CO₃ at about 850 °C to give sodium metavanadate (NaVO₃). An aqueous extract of this solid is acidified to produce "red cake", a polyvanadate salt, which is reduced with calcium metal. As an alternative for small-scale production, vanadium pentoxide is reduced with hydrogen or magnesium. Many other methods are also used, in all of which vanadium is produced as a byproduct of other processes.{{cite journal|journal= Minerals Engineering|volume= 16|pages= 793–805|doi= 10.1016/S0892-6875(03)00213-9|first= R. R.|last= Moskalyk|author2=Alfantazi, A. M. |title= Processing of vanadium: a review|date= 2003|issue= 9|bibcode= 2003MiEng..16..793M}} Purification of vanadium is possible by the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925. It involves the formation of the metal iodide, in this example vanadium(III) iodide, and the subsequent decomposition to yield pure metal:{{cite journal|title= Preparation of High-Purity Vanadium Metals by the Iodide Refining Process|journal= Journal of the Electrochemical Society|volume= 108|page=88|date= 1961|first= O. N.|last= Carlson|author2=Owen, C. V. |doi= 10.1149/1.2428019}}

:2 V + 3 I₂ {{eqm}} 2 VI₃

File:FerroVanadium.jpg

Most vanadium is used as a component of a steel alloy called ferrovanadium. Ferrovanadium is produced directly by reducing a mixture of vanadium oxide, iron oxides and iron in an electric furnace. The vanadium ends up in pig iron produced from vanadium-bearing magnetite. Depending on the ore used, the slag contains up to 25% of vanadium.

Approximately 70000 tonnes of vanadium ore are produced yearly, with 25000 t of vanadium ore being produced in Russia, 24000 in South Africa, 19000 in China, and 1000 in Kazakhstan. 7000 t of vanadium metal are produced each year. It is impossible to obtain vanadium by heating its ore with carbon. Instead, vanadium is produced by heating vanadium oxide with calcium in a pressure vessel. Very high-purity vanadium is produced from a reaction of vanadium trichloride with magnesium.

After the separation from the other minerals, the mixed oxides of tantalum tantalum pentoxide and niobium Niobium pentoxide are obtained. To produce niobium, the first step in the processing is the reaction of the oxides with hydrofluoric acid:

:{{chem2|Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O}}

:{{chem2|Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O}}

The first industrial scale separation, developed by Swiss chemist de Marignac, exploits the differing solubilities of the complex niobium and tantalum fluorides, dipotassium oxypentafluoroniobate monohydrate ({{chem2|K2[NbOF5]*H2O}}) and dipotassium heptafluorotantalate ({{chem2|K2[TaF7]}}) in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like cyclohexanone. The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water and either precipitated by the addition of potassium fluoride to produce a potassium fluoride complex, or precipitated with ammonia as the pentoxide:

:{{chem2|H2[NbOF5] + 2 KF → K2[NbOF5]↓ + 2 HF}}

Followed by:

:{{chem2|2 H2[NbOF5] + 10 NH4OH → Nb2O5↓ + 10 NH4F + 7 H2O}}

Several methods are used for the reduction to metallic niobium. The electrolysis of a molten mixture of {{chem2|K2}}[{{chem2|NbOF5}}] and sodium chloride is one; the other is the reduction of the fluoride with sodium. With this method, a relatively high purity niobium can be obtained. In large scale production, {{chem2|Nb2O5}} is reduced with hydrogen or carbon. In the aluminothermic reaction, a mixture of iron oxide and niobium oxide is reacted with aluminium:

:{{chem2|3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3}}

Small amounts of oxidizers like sodium nitrate are added to enhance the reaction. The result is aluminium oxide and ferroniobium, an alloy of iron and niobium used in steel production.{{cite book|title = Progress in Niobium Markets and Technology 1981–2001|author = Tither, Geoffrey|url = https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/images/pdfs/oppening.pdf|journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA)|date = 2001|isbn = 978-0-9712068-0-9|editor = Minerals, Metals and Materials Society|url-status = dead|archive-url = https://web.archive.org/web/20081217100553/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/images/pdfs/oppening.pdf|archive-date = 17 December 2008|df = dmy-all}}{{cite book|title=The Production of Ferroniobium at the Niobec mine 1981–2001 |first=Claude |last=Dufresne |author2=Goyette, Ghislain |url=https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/sub_1/images/pdfs/start.pdf |journal=Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |date=2001 |isbn=978-0-9712068-0-9 |editor = Minerals, Metals and Materials Society |url-status=dead |archive-url=https://web.archive.org/web/20081217100559/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_1/images/pdfs/start.pdf |archive-date=17 December 2008 }} Ferroniobium contains between 60 and 70% niobium.{{cite web|url = http://tesla.desy.de/new_pages/TESLA_Reports/2001/pdf_files/tesla2001-27.pdf|title = Niob für TESLA|access-date = 2 September 2008|first = J.|last = Kouptsidis|author2 = Peters, F.|author3 = Proch, D.|author4 = Singer, W.|publisher = Deutsches Elektronen-Synchrotron DESY|language = de|url-status = dead|archive-url = https://web.archive.org/web/20081217100548/http://tesla.desy.de/new_pages/TESLA_Reports/2001/pdf_files/tesla2001-27.pdf|archive-date = 17 December 2008|df = dmy-all}} Without iron oxide, the aluminothermic process is used to produce niobium. Further purification is necessary to reach the grade for superconductive alloys. Electron beam melting under vacuum is the method used by the two major distributors of niobium.{{cite journal|journal = The Iron and Steel Institute of Japan International|volume = 32|date = 1992|issue = 5|doi = 10.2355/isijinternational.32.673|title = Electron Beam Melting and Refining of Metals and Alloys|first = Alok|last = Choudhury|author2=Hengsberger, Eckart |pages = 673–681|doi-access = free}}

{{as of|2013}}, CBMM from Brazil controlled 85 percent of the world's niobium production.{{Citation

|last1=Lucchesi |first1=Cristane |last2=Cuadros|first2=Alex |date=April 2013 |title=Mineral Wealth |type=paper |magazine=Bloomberg Markets |page=14}} The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500{{Nbsp}}tonnes in 2006.{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs06.pdf |title=Niobium (Columbium) |first=John F. |last=Papp |publisher=USGS 2006 Commodity Summary |access-date=20 November 2008 |archive-date=17 December 2008 |archive-url=https://web.archive.org/web/20081217100548/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs06.pdf |url-status=live }}{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs07.pdf |title=Niobium (Columbium) |first=John F. |last=Papp |publisher=USGS 2007 Commodity Summary |access-date=20 November 2008 |archive-date=5 August 2017 |archive-url=https://web.archive.org/web/20170805170910/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs07.pdf |url-status=live }} Worldwide resources are estimated to be 4.4 million tonnes. During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/niobium/230397.pdf|title = Niobium (Columbium)|first = John F.|last = Papp|publisher = USGS 1997 Commodity Summary|access-date = 20 November 2008|archive-date = 11 January 2019|archive-url = https://web.archive.org/web/20190111003407/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/230397.pdf|url-status = live}} Between 2009 and 2011, production was stable at 63,000{{Nbsp}}tonnes per year,[http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2011-niobi.pdf Niobium (Colombium)] {{Webarchive|url=https://web.archive.org/web/20120708152542/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2011-niobi.pdf |date=8 July 2012 }} U.S. Geological Survey, Mineral Commodity Summaries, January 2011 with a slight decrease in 2012 to only 50,000{{Nbsp}}tonnes per year.[http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2016-niobi.pdf Niobium (Colombium)] {{Webarchive|url=https://web.archive.org/web/20160306095041/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2016-niobi.pdf |date=6 March 2016 }} U.S. Geological Survey, Mineral Commodity Summaries, January 2016

70,000{{Nbsp}}tonnes of tantalum ore are produced yearly. Brazil produces 90% of tantalum ore, with Canada, Australia, China, and Rwanda also producing the element. The demand for tantalum is around 1,200{{Nbsp}}tonnes per year.

Dubnium is produced synthetically by bombarding actinides with lighter elements. To date, no experiments in a supercollider have been conducted to synthesize the next member of the group, either unpentseptium (Ups) or unpentennium (Upe). As unpentseptium and unpentennium are both late period 8 elements, it is unlikely that these elements will be synthesized in the near future; current attempts have only been made on elements up to atomic number 127.{{cite book |last=Emsley |first=John |title=Nature's Building Blocks: An A-Z Guide to the Elements |publisher=Oxford University Press |year=2011 |isbn=978-0-19-960563-7 |edition=New |location=New York, NY |page=588}}

File:Sink and taps in the men's locker room 3 BW.jpg

Vanadium's main application is in alloys, such as vanadium steel. Vanadium alloys are used in springs, tools, jet engines, armor plating, and nuclear reactors. Vanadium oxide gives ceramics a golden color, and other vanadium compounds are used as catalysts to produce polymers.

Small amounts of niobium are added to stainless steel to improve its quality. Niobium alloys are also used in rocket nozzles because of niobium's high corrosion resistance.

Tantalum has four main types of applications. Tantalum is added into objects exposed to high temperatures, in electronic devices, in surgical implants, and for handling corrosive substances.

Dubnium has no applications due to the difficulty of its synthesis and the very short half-lives of even its longest-lived isotopes.{{Cite book |last1=Karpov |first1=A. V. |title=Exciting Interdisciplinary Physics |last2=Zagrebaev |first2=V. I. |last3=Palenzuela |first3=Y. M. |last4=Greiner |first4=W. |date=2013 |publisher=Springer International Publishing |isbn=978-3-319-00046-6 |editor-last=Greiner |editor-first=W. |series=FIAS Interdisciplinary Science Series |pages=69–79 |language=en |article=Superheavy Nuclei: Decay and Stability |doi=10.1007/978-3-319-00047-3_6}}

{{main|Vanadium#Biological role}}

Out of the group 5 elements, only vanadium has been identified as playing a role in the biological chemistry of living systems, but even it plays a very limited role in biology, and is more important in ocean environments than on land.

File:Bluebell_tunicates_Nick_Hobgood.jpg such as this bluebell tunicate contain vanadium as vanabins.]]

Vanadium, essential to ascidians and tunicates as vanabins, has been known in the blood cells of Ascidiacea (sea squirts) since 1911,{{cite journal|last1=Henze|first1=M.|title=Untersuchungen über das Blut der Ascidien. I. Mitteilung. Die Vanadiumverbindung der Blutkörperchen|journal=Hoppe-Seyler's Zeitschrift für Physiologische Chemie|date=1911|volume=72|issue=5–6|pages=494–501|doi=10.1515/bchm2.1911.72.5-6.494|language=de|url=https://zenodo.org/record/1448780}}{{cite journal | doi = 10.1002/jemt.10042 | last1 = Michibata | first1 = H | last2 = Uyama | first2 = T | last3 = Ueki | first3 = T | last4 = Kanamori | first4 = K | name-list-style = vanc | year = 2002 | title = Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians | url = http://ir.lib.hiroshima-u.ac.jp/files/public/0/22/20141016115442843522/MicroscopResTech_56_421-434_2002.pdf | journal = Microscopy Research and Technique | volume = 56 | issue = 6 | pages = 421–434 | pmid = 11921344 | s2cid = 15127292 | access-date = 26 June 2019 | archive-date = 17 March 2020 | archive-url = https://web.archive.org/web/20200317132408/https://ir.lib.hiroshima-u.ac.jp/files/public/0/22/20141016115442843522/MicroscopResTech_56_421-434_2002.pdf | url-status = dead }} in concentrations of vanadium in their blood more than 100 times higher than the concentration of vanadium in the seawater around them. Several species of macrofungi accumulate vanadium (up to 500 mg/kg in dry weight).{{cite journal|last1=Kneifel|first1=Helmut |last2=Bayer|first2=Ernst |year=1997|title=Determination of the Structure of the Vanadium Compound, Amavadine, from Fly Agaric|journal=Angewandte Chemie International Edition in English|volume=12|issue=6|pages=508|issn=1521-3773|doi=10.1002/anie.197305081}} Vanadium-dependent bromoperoxidase generates organobromine compounds in a number of species of marine algae.{{Cite journal|journal = Natural Product Reports|year = 2004|volume = 21|issue = 1|pmid = 15039842|doi = 10.1039/b302337k|title = The role of vanadium bromoperoxidase in the biosynthesis of halogenated marine natural products|first1 = Alison|last1 = Butler|last2= Carter-Franklin|first2=Jayme N.|pages = 180–8}}

Rats and chickens are also known to require vanadium in very small amounts and deficiencies result in reduced growth and impaired reproduction.{{cite journal|title = Growth Effects of Vanadium in the Rat|first1 = Klaus|last1 = Schwarz|last2=Milne|first2=David B.|journal = Science|volume = 174|issue = 4007|year = 1971|pages = 426–428|jstor = 1731776|doi = 10.1126/science.174.4007.426|pmid = 5112000|bibcode = 1971Sci...174..426S | s2cid=24362265 }} Vanadium is a relatively controversial dietary supplement, primarily for increasing insulin sensitivity{{cite journal|journal = Diabetes Care|volume = 26|pages = 1277–1294|year = 2003|title = Systematic Review of Herbs and Dietary Supplements for Glycemic Control in Diabetes|first1 = Gloria Y.|last1 = Yeh|last2= Eisenberg|first2=David M.|last3=Kaptchuk|first3=Ted J.|last4=Phillips|first4=Russell S.|url = http://care.diabetesjournals.org/cgi/content/full/26/4/1277|doi = 10.2337/diacare.26.4.1277|pmid = 12663610|issue = 4|doi-access = free}} and body-building. Vanadyl sulfate may improve glucose control in people with type 2 diabetes.{{cite journal| journal = The Journal of Alternative and Complementary Medicine| volume = 5| year = 1999| pages = 273–291| title = Vanadium: a review of its potential role in the fight against diabetes| last1 = Badmaev| first1 = V.| doi = 10.1089/acm.1999.5.273| last2 = Prakash| first2 = Subbalakshmi| last3 = Majeed| first3 = Muhammed| pmid=10381252| issue = 3}} In addition, decavanadate and oxovanadates are species that potentially have many biological activities and that have been successfully used as tools in the comprehension of several biochemical processes.{{cite journal|journal = Journal of Inorganic Biochemistry| volume = 103|pages = 536–546|year = 2009|title = Decavanadate and oxovanadates: Oxometalates with many biological activities|first1 = Manuel|last1 = Aureliano| last2=Crans|first2=Debbie C.| issue = 4| doi = 10.1016/j.jinorgbio.2008.11.010| pmid = 19110314}}

Pure vanadium is not known to be toxic. However, vanadium pentoxide causes severe irritation of the eyes, nose, and throat. Tetravalent VOSO₄ has been reported to be at least 5 times more toxic than trivalent V₂O₃.{{cite journal|last= Roschin|first= A. V.|date= 1967|title= Toxicology of vanadium compounds used in modern industry|journal= Gig Sanit. (Water Res.)|volume= 32|issue= 6|pages= 26–32|pmid= 5605589}} The Occupational Safety and Health Administration has set an exposure limit of 0.05 mg/m³ for vanadium pentoxide dust and 0.1 mg/m³ for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week.{{cite web|url= http://www.osha.gov/SLTC/healthguidelines/vanadiumpentoxidedust/recognition.html|title= Occupational Safety and Health Guidelines for Vanadium Pentoxide|publisher= Occupational Safety and Health Administration|access-date= 29 January 2009|url-status= dead|archive-url= https://web.archive.org/web/20090106063227/http://www.osha.gov/SLTC/healthguidelines/vanadiumpentoxidedust/recognition.html|archive-date= 6 January 2009}} The National Institute for Occupational Safety and Health has recommended that 35 mg/m³ of vanadium be considered immediately dangerous to life and health, that is, likely to cause permanent health problems or death. Vanadium compounds are poorly absorbed through the gastrointestinal system. Inhalation of vanadium and vanadium compounds results primarily in adverse effects on the respiratory system.{{cite book|last= Sax|first= N. I.|date= 1984|title= Dangerous Properties of Industrial Materials|edition= 6th|publisher= Van Nostrand Reinhold Company|pages= 2717–2720}}{{cite journal|title= Nanoparticulate Vanadium Oxide Potentiated Vanadium Toxicity in Human Lung Cells|author= Wörle-Knirsch, Jörg M. |author2= Kern, Katrin |author3= Schleh, Carsten |author4= Adelhelm, Christel |author5= Feldmann, Claus |author6= Krug, Harald F. |name-list-style= amp|journal= Environ. Sci. Technol. |date= 2007|volume= 41|pages= 331–336|doi= 10.1021/es061140x|pmid= 17265967|issue= 1|bibcode= 2007EnST...41..331W}} Quantitative data are, however, insufficient to derive a subchronic or chronic inhalation reference dose. Other effects have been reported after oral or inhalation exposures on blood parameters,{{cite journal |last=Ścibior |first=A. |author2=Zaporowska, H. |author3=Ostrowski, J. |date=2006 |title=Selected haematological and biochemical parameters of blood in rats after subchronic administration of vanadium and/or magnesium in drinking water |journal=Archives of Environmental Contamination and Toxicology |volume=51 |issue=2 |pages=287–295 |doi=10.1007/s00244-005-0126-4 |pmid=16783625|bibcode=2006ArECT..51..287S |s2cid=43805930 }}{{cite journal |last=Gonzalez-Villalva |first=A. |display-authors=etal |date= 2006|title=Thrombocytosis induced in mice after subacute and subchronic V2O5 inhalation |journal=Toxicology and Industrial Health |volume=22 |issue=3 |pages=113–116 |doi=10.1191/0748233706th250oa |pmid=16716040|bibcode=2006ToxIH..22..113G |s2cid=9986509 }} liver,{{cite journal|journal= Toxicology|volume= 228|date= 2006|pages= 162–170|doi= 10.1016/j.tox.2006.08.022|title= Pentavalent vanadium induces hepatic metallothionein through interleukin-6-dependent and -independent mechanisms|author= Kobayashi, Kazuo|pmid= 16987576|issue= 2–3|last2= Himeno|first2= Seiichiro|last3= Satoh|first3= Masahiko|last4= Kuroda|first4= Junji|last5= Shibata|first5= Nobuo|last6= Seko|first6= Yoshiyuki|last7= Hasegawa|first7= Tatsuya|bibcode= 2006Toxgy.228..162K}} neurological development,{{cite journal |last=Soazo |first=Marina |author2=Garcia, Graciela Beatriz |date=2007 |title=Vanadium exposure through lactation produces behavioral alterations and CNS myelin deficit in neonatal rats |journal=Neurotoxicology and Teratology |volume=29 |issue=4 |pages=503–510 |doi=10.1016/j.ntt.2007.03.001 |pmid=17493788|bibcode=2007NTxT...29..503S }} and other organs{{cite journal|last= Barceloux|first= Donald G.|author2=Barceloux, Donald |date= 1999|title= Vanadium|journal= Clinical Toxicology|volume= 37|issue= 2|pages= 265–278|doi= 10.1081/CLT-100102425|pmid= 10382561}} in rats.

There is little evidence that vanadium or vanadium compounds are reproductive toxins or teratogens. Vanadium pentoxide was reported to be carcinogenic in male rats and in male and female mice by inhalation in an NTP study,{{cite journal |last=Ress |first=N. B. |display-authors=etal |date=2003 |title=Carcinogenicity of inhaled vanadium pentoxide in F344/N rats and B6C3F1 mice |journal=Toxicological Sciences |volume=74 |issue=2 |pages=287–296 |doi=10.1093/toxsci/kfg136 |pmid=12773761|doi-access=free }} although the interpretation of the results has recently been disputed.{{cite journal |last=Duffus |first=J. H. |date=2007 |title=Carcinogenicity classification of vanadium pentoxide and inorganic vanadium compounds, the NTP study of carcinogenicity of inhaled vanadium pentoxide, and vanadium chemistry |journal=Regulatory Toxicology and Pharmacology |volume=47 |issue=1 |pages=110–114 |doi=10.1016/j.yrtph.2006.08.006 |pmid=17030368}} The carcinogenicity of vanadium has not been determined by the United States Environmental Protection Agency.{{cite web|url= https://rais.ornl.gov/tox/profiles/vanadium_f_V1.html|title= Toxicity Summary for Vanadium|date= 1991|first= Dennis M.|last= Opreskos |access-date=8 November 2008 |publisher= Oak Ridge National Laboratory}} Vanadium traces in diesel fuels are the main fuel component in high temperature corrosion. During combustion, vanadium oxidizes and reacts with sodium and sulfur, yielding vanadate compounds with melting points as low as 530 °C, which attack the passivation layer on steel and render it susceptible to corrosion. The solid vanadium compounds also abrade engine components.{{cite book |page= 92 |url= https://books.google.com/books?id=RC_k4q6y-JIC&pg=PA92 |title= Pounder's Marine Diesel Engines and Gas Turbines |isbn= 9780080943619 |last1= Woodyard |first1= Doug |date= 2009-08-18| publisher=Butterworth-Heinemann }}{{cite book |page= 152 |url= https://books.google.com/books?id=J_AkNu-Y1wQC&pg=PA152 |title= Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing |isbn= 9780803120969 |last1= Totten |first1= George E. |last2= Westbrook |first2= Steven R. |last3= Shah |first3= Rajesh J. |date= 2003-06-01}}

Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants.{{cite journal|title = New trends in the use of metals in jewellery|author=Vilaplana, J.|author2=Romaguera, C.|author3=Grimalt, F.|author4=Cornellana, F.|journal = Contact Dermatitis|volume = 25|issue = 3 |pages = 145–148|date = 1990|doi = 10.1111/j.1600-0536.1991.tb01819.x|pmid = 1782765|s2cid=30201028|doi-access = }}{{cite journal|title = New developments in jewellery and dental materials|first = J.|last = Vilaplana|author2=Romaguera, C. | journal = Contact Dermatitis|volume = 39|issue = 2| pages = 55–57|date = 1998|doi = 10.1111/j.1600-0536.1998.tb05832.x|pmid = 9746182|s2cid = 34271011}} Niobium and its compounds thought to be slightly toxic. Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD{{sub|50}}) between 10 and 100 mg/kg.{{cite journal|title = Pharmacology and toxicology of niobium chloride|author=Haley, Thomas J.|author2=Komesu, N.|author3=Raymond, K.|journal = Toxicology and Applied Pharmacology|volume = 4|issue = 3|pages = 385–392|date = 1962|doi = 10.1016/0041-008X(62)90048-0|pmid=13903824|bibcode=1962ToxAP...4..385H }}{{cite journal|title = The Toxicity of Niobium Salts |author=Downs, William L. |display-authors=4 |author2=Scott, James K. |author3=Yuile, Charles L. |author4=Caruso, Frank S. |author5=Wong, Lawrence C. K.|journal = American Industrial Hygiene Association Journal|volume = 26|issue = 4|pages = 337–346|date = 1965|doi = 10.1080/00028896509342740|pmid = 5854670}}{{cite journal|title = Zirconium, Niobium, Antimony, Vanadium and Lead in Rats: Life term studies|author=Schroeder, Henry A.|author2=Mitchener, Marian|author3=Nason, Alexis P.|journal = Journal of Nutrition|volume = 100|issue = 1|pages = 59–68|date=1970|pmid =5412131|doi=10.1093/jn/100.1.59|s2cid=4444415|url = https://pdfs.semanticscholar.org/7730/157588b8312d9076f95fcfb78d404a893033.pdf|archive-url = https://web.archive.org/web/20200219052439/https://pdfs.semanticscholar.org/7730/157588b8312d9076f95fcfb78d404a893033.pdf|url-status = dead|archive-date = 2020-02-19}} For oral administration the toxicity is lower; a study with rats yielded a LD{{sub|50}} after seven days of 940 mg/kg.

Compounds containing tantalum are rarely encountered in the laboratory, and it and its compounds rarely cause injury, and when they do, the injuries are normally rashes. The metal is highly biocompatible{{cite journal|journal = Canadian Medical Association Journal |first = Gerald L. |last = Burke |date = 1940 |title =The Corrosion of Metals in Tissues; and An Introduction to Tantalum |volume = 43|issue = 2 |pages = 125–128 |pmid = 20321780 |pmc = 538079 }} and is used for body implants and coatings, therefore attention may be focused on other elements or the physical nature of the chemical compound.{{cite journal|journal = Biomaterials|author = Matsuno H|author2 = Yokoyama A|author3 = Watari F|author4 = Uo M|author5 = Kawasaki T.|date = 2001|volume = 22|title = Biocompatibility and osteogenesis of refractory metal implants, titanium, hafnium, niobium, tantalum and rhenium. Biocompatibility of tantalum.|doi = 10.1016/S0142-9612(00)00275-1|pmid=11336297|issue = 11|pages = 1253–62}} People can be exposed to tantalum in the workplace by breathing it in, skin contact, or eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for tantalum exposure in the workplace as 5 mg/m³ over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit of 5 mg/m³ over an 8-hour workday and a short-term limit of 10 mg/m³. At levels of 2500 mg/m³, tantalum is immediately dangerous to life and health.{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Tantalum (metal and oxide dust, as Ta)|url = https://www.cdc.gov/niosh/npg/npgd0585.html|website = www.cdc.gov|access-date = 2015-11-24}}

{{notelist}}

{{reflist}}

• {{cite journal | doi =10.1016/S0920-5861(02)00318-8 | title =Vanadium to dubnium: from confusion through clarity to complexity | year =2003 | last1 =Greenwood | first1 =N | journal =Catalysis Today | volume =78 | issue =1–4 | pages =5–11}}

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