Editing Niobium (section)

==Characteristics==
===Physical===
Niobium is a [[lustre (mineralogy)|lustrous]], grey, [[ductility|ductile]], [[paramagnetism|paramagnetic]] [[metal]] in [[Group 5 element|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}}</ref>

{| class="wikitable"  style="margin:10px; float:right;"
|-
![[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]]
|-
| 23 || [[vanadium]] || 2, 8, 11, 2
|-
| 41 || niobium || 2, 8, 18, 12, 1
|-
| 73 || [[tantalum]] || 2, 8, 18, 32, 11, 2
|-
| 105 || [[dubnium]] || 2, 8, 18, 32, 32, 11, 2
|}

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" /><!--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>

===Chemical===
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods.<ref name="Rubber">{{cite book|title = CRC Handbook of Chemistry and Physics|first = David R.|last = Lide|publisher = CRC Press|date = 2004|isbn = 978-0-8493-0485-9|pages = '''4'''–21|edition = 85th|chapter = The Elements|chapter-url-access = registration|chapter-url = https://archive.org/details/crchandbookofche81lide|url = https://archive.org/details/crchandbookofche81lide|url-access = registration}}</ref> Despite a high melting point in elemental form (2,468&nbsp;°C), it is less dense than other [[refractory metals]]. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms [[dielectric]] [[oxide]] layers.

Niobium is slightly less [[electropositive]] and more compact than its predecessor in the periodic table, [[zirconium]], whereas it is virtually identical in size to the heavier tantalum atoms, as a result of the [[lanthanide contraction]].<ref name="Nowak" /> As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the [[periodic table]].<ref name="Gupta">{{cite book|title = Extractive Metallurgy of Niobium|first = C. K.|last = Gupta|author2=Suri, A. K. |publisher = CRC Press|date = 1994 |isbn = 978-0-8493-6071-8|pages = 1–16}}</ref> Although its corrosion resistance is not as outstanding as that of tantalum, the lower price and greater availability make niobium attractive for less demanding applications, such as vat linings in chemical plants.<ref name="Nowak" />

===Isotopes===
{{main|Isotopes of niobium}}
Almost all of the niobium in Earth's crust is the one stable [[isotope]], {{sup|93}}Nb.<ref name="NUBASE">{{NUBASE 2003}}</ref> By 2003, at least 32 [[radioisotope]]s had been synthesized, ranging in [[atomic mass]] from 81 to 113. The most stable is {{sup|92}}Nb with [[half-life]] 34.7&nbsp;million years. {{Sup|92}}Nb, along with {{sup|94}}Nb, has been detected in refined samples of terrestrial niobium and may originate from bombardment by [[cosmic ray]] [[muon]]s in Earth's crust.<ref>{{cite journal|last1=Clayton|first1=Donald D.|last2=Morgan|first2=John A.|date=1977|journal=Nature|volume=266|issue=5604|pages=712–713|title=Muon production of <sup>92,94</sup>Nb in the Earth's crust|doi=10.1038/266712a0|s2cid=4292459}}</ref> One of the least stable niobium isotopes is <sup>113</sup>Nb; estimated half-life 30&nbsp;milliseconds. Isotopes lighter than the stable {{sup|93}}Nb tend to [[beta decay|β{{sup|+}} decay]], and those that are heavier tend to β{{sup|−}} decay, with some exceptions. {{sup|81}}Nb, {{sup|82}}Nb, and {{sup|84}}Nb have minor β{{sup|+}}-delayed [[proton emission]] decay paths, {{sup|91}}Nb decays by [[electron capture]] and [[positron emission]], and {{sup|92}}Nb decays by both [[positron|β{{sup|+}}]] and [[electron|β{{sup|−}}]] decay.<ref name="NUBASE" />

At least 25 [[nuclear isomer]]s have been described, ranging in atomic mass from 84 to 104. Within this range, only {{sup|96}}Nb, {{sup|101}}Nb, and {{sup|103}}Nb do not have isomers. The most stable of niobium's isomers is {{sup|93m}}Nb with half-life 16.13&nbsp;years. The least stable isomer is {{sup|84m}}Nb with a half-life of 103&nbsp;ns. All of niobium's isomers decay by [[isomeric transition]] or beta decay except {{sup|92m1}}Nb, which has a minor electron capture branch.<ref name="NUBASE" />

===Occurrence===
{{see also|Category:Niobium minerals}}
Niobium is estimated to be the [[Abundance of elements in Earth's crust|33rd most abundant element in the Earth's crust]], at 20&nbsp;[[Parts per million|ppm]].<ref>{{cite book|title = Nature's Building Blocks: An A-Z Guide to the Elements|last = Emsley|first = John|publisher = Oxford University Press|date = 2001|location = Oxford, England|isbn = 978-0-19-850340-8|chapter = Niobium|pages = [https://archive.org/details/naturesbuildingb0000emsl/page/283 283–286]|chapter-url = https://archive.org/details/naturesbuildingb0000emsl/page/283}}</ref> Some believe that the abundance on Earth is much greater, and that the element's high density has concentrated it in Earth's core.<ref name="patel" /> The free element is not found in nature, but niobium occurs in combination with other elements in minerals.<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> Minerals that contain niobium often also contain tantalum. Examples include [[Ferrocolumbite|columbite]] ({{chem2|(Fe,Mn)Nb2O6}}) and [[coltan|columbite–tantalite]] (or ''coltan'', {{chem2|(Fe,Mn)(Ta,Nb)2O6}}).<ref name="ICE" /> Columbite–tantalite minerals (the most common species being columbite-(Fe) and tantalite-(Fe), where "-(Fe)" is the Levinson suffix indicating the prevalence of iron over other elements such as manganese<ref>{{Cite web|url=https://www.mindat.org/min-1514.html|title=Columbite-(Fe): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=18 March 2017|archive-url=https://web.archive.org/web/20170318085151/https://www.mindat.org/min-1514.html|url-status=live}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-1530.html|title=Tantalite-(Fe): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=6 November 2018|archive-url=https://web.archive.org/web/20181106004948/https://www.mindat.org/min-1530.html|url-status=live}}</ref><ref name="Burke">{{cite journal |journal=Elements |last1=Burke |first1=Ernst A.J. |title=The use of suffixes in mineral names |url=http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf |date=2008 |volume=4 |issue=2 |page=96 |access-date=7 December 2019 |archive-date=19 December 2019 |archive-url=https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf |url-status=live }}</ref><ref name="nrmima.nrm.se">{{Cite web|url=http://nrmima.nrm.se/|title=CNMNC|website=nrmima.nrm.se|access-date=6 October 2018|archive-url=https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//|archive-date=10 August 2019|url-status=dead}}</ref>) that are most usually found as accessory minerals in [[pegmatite]] intrusions, and in [[alkali]]ne [[intrusive rock]]s. Less common are the niobates of [[calcium]], [[uranium]], [[thorium]] and the [[rare earth element]]s. Examples of such niobates are [[pyrochlore]] ({{chem2|(Na,Ca)2Nb2O6(OH,F)}}) (now a group name, with a relatively common example being, e.g., fluorcalciopyrochlore<ref name="Burke" /><ref name="nrmima.nrm.se" /><ref>{{Cite web|url=https://www.mindat.org/min-3316.html|title=Pyrochlore Group: Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=19 June 2018|archive-url=https://web.archive.org/web/20180619113047/https://www.mindat.org/min-3316.html|url-status=live}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-40341.html|title=Fluorcalciopyrochlore: Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=28 September 2018|archive-url=https://web.archive.org/web/20180928043940/https://www.mindat.org/min-40341.html|url-status=live}}</ref><ref>{{cite journal |url=http://rruff.info/uploads/AM62_403.pdf |title=Classification and nomenclatureof the pyrochlore group |last=Hogarth |first=D. D. |date=1977 |journal=American Mineralogist |volume=62 |pages=403–410 |archive-url=https://web.archive.org/web/20181105030236/http://rruff.info/uploads/AM62_403.pdf |archive-date=5 November 2018}}</ref>) and [[euxenite]] (correctly named euxenite-(Y)<ref name="Burke" /><ref name="nrmima.nrm.se" /><ref>{{Cite web|url=https://www.mindat.org/min-1425.html|title=Euxenite-(Y): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=7 October 2018|archive-url=https://web.archive.org/web/20181007040042/https://www.mindat.org/min-1425.html|url-status=live}}</ref>) ({{chem2|(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6}}). These large deposits of niobium have been found associated with [[carbonatite]]s [[carbonate minerals|(carbonate]]-[[silicate]] [[igneous rocks]]) and as a constituent of pyrochlore.<ref name="Pyrochlore">{{cite journal|title = Geochemical alteration of pyrochlore group minerals: Pyrochlore subgroup|date = 1995|first = Gregory R.|last = Lumpkin|author2 = Ewing, Rodney C.|journal = American Mineralogist|url = http://www.minsocam.org/msa/AmMin/TOC/Articles_Free/1995/Lumpkin_p732-743_95.pdf|volume = 80|issue = 7–8|pages = 732–743|bibcode = 1995AmMin..80..732L|doi = 10.2138/am-1995-7-810|s2cid = 201657534|access-date = 14 October 2008|archive-date = 17 December 2008|archive-url = https://web.archive.org/web/20081217100545/http://www.minsocam.org/msa/AmMin/TOC/Articles_Free/1995/Lumpkin_p732-743_95.pdf|url-status = live}}</ref> <!--http://minmag.geoscienceworld.org/cgi/content/abstract/64/4/683 -->

The three largest currently mined deposits of pyrochlore, two in Brazil and one in Canada, were found in the 1950s, and are still the major producers of niobium mineral concentrates.<ref name="Gupta" /> The largest deposit is hosted within a [[carbonatite]] [[Igneous intrusion|intrusion]] in [[Araxá]], state of [[Minas Gerais]], Brazil, owned by CBMM ([[Companhia Brasileira de Metalurgia e Mineração]]); the other active Brazilian deposit is located near [[Catalão]], state of [[Goiás]], and owned by [[China Molybdenum]], also hosted within a carbonatite intrusion.<ref name="tesla" /> Together, those two mines produce about 88% of the world's supply.<ref name="g1">{{cite news |last=Alvarenga |first=Darlan |url=http://g1.globo.com/economia/negocios/noticia/2013/04/monopolio-brasileiro-do-niobio-gera-cobica-mundial-controversia-e-mitos.html |title='Monopólio' brasileiro do nióbio gera cobiça mundial, controvérsia e mitos |language=pt |trans-title=Brazilian niobium 'monopoly' brings about the world's greed, controversy, and myths |work=[[G1 (website)|G1]] |location=São Paulo |date=9 April 2013 |access-date=23 May 2016 |archive-date=29 May 2016 |archive-url=https://web.archive.org/web/20160529175614/http://g1.globo.com/economia/negocios/noticia/2013/04/monopolio-brasileiro-do-niobio-gera-cobica-mundial-controversia-e-mitos.html |url-status=live }}</ref> Brazil also has a large but still unexploited deposit near [[São Gabriel da Cachoeira]], state of [[Amazonas (Brazilian state)|Amazonas]], as well as a few smaller deposits, notably in the state of [[Roraima]].<ref name="g1" /><ref name="rio negro">{{cite journal|last1=Siqueira-Gay|first1=Juliana |last2=Sánchez| first2=Luis E.|title =Keep the Amazon niobium in the ground|journal= Environmental Science & Policy|volume=111|year= 2020|pages= 1–6|issn=1462-9011|doi =10.1016/j.envsci.2020.05.012 |bibcode=2020ESPol.111....1S |s2cid=219469278 }}</ref>

The third largest producer of niobium is the carbonatite-hosted [[Niobec]] mine, in [[Saint-Honoré, Quebec|Saint-Honoré]], near [[Chicoutimi]], [[Quebec]], Canada, owned by Magris Resources.<ref name="niobec-magris">{{cite press release |url=http://niobec.com/en/2015/01/magris-resources-officially-owner-of-niobec/ |title=Magris Resources, officially owner of Niobec |publisher=Niobec |date=23 January 2015 |access-date=23 May 2016 |archive-date=5 June 2016 |archive-url=https://web.archive.org/web/20160605092511/http://niobec.com/en/2015/01/magris-resources-officially-owner-of-niobec/ |url-status=live }}</ref> It produces between 7% and 10% of the world's supply.<ref name="tesla">{{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}}</ref><ref name="g1" />