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{{infobox molybdenum}}
'''Molybdenum''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Mo''' (from [[Neo-Latin]] ''molybdaenum'') and [[atomic number]] 42. The name derived from [[Ancient Greek]] {{lang|grc|Μόλυβδος}} ''{{transliteration|grc|molybdos}}'', meaning [[lead]], since its ores were confused with lead ores.<ref name="CRCdescription2">{{Cite book|title=CRC Handbook of Chemistry and Physics|date=1994|publisher=Chemical Rubber Publishing Company|isbn=978-0-8493-0474-3|editor=Lide, David R.|volume=4|page=18|contribution=Molybdenum}}</ref> Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by [[Carl Wilhelm Scheele]]. The metal was first isolated in 1781 by [[Peter Jacob Hjelm]].<ref>{{Cite web|title=It's Elemental – The Element Molybdenum|url=https://education.jlab.org/itselemental/ele042.html|url-status=live|archive-url=https://web.archive.org/web/20180704035201/https://education.jlab.org/itselemental/ele042.html|archive-date=2018-07-04|access-date=2018-07-03|website=Science Education at Jefferson Lab |language=en-us}}</ref>

Molybdenum does not occur naturally as a [[Native metal|free metal]] on Earth; in its minerals, it is found only in [[oxidation state|oxidized state]]s. The free element, a silvery [[metal]] with a grey cast, has the [[List of elements by melting point|sixth-highest]] [[melting point]] of any element. It readily forms hard, stable [[carbide]]s in [[alloy]]s, and for this reason most of the world production of the element (about 80%) is used in [[steel]] alloys, including high-strength alloys and [[superalloy]]s.

Most molybdenum compounds have low [[solubility]] in water.  Heating molybdenum-bearing minerals under [[oxygen]] and water affords [[molybdate]] ion {{chem|MoO|4|2-}}, which forms quite soluble salts. Industrially, molybdenum [[Chemical compound|compounds]] (about 14% of world production of the element) are used as [[pigment]]s and [[Catalysis|catalysts]].

{{c|Molybdenum enzymes|Molybdenum-bearing enzymes}} are by far the most common bacterial catalysts for breaking the [[chemical bond]] in atmospheric molecular [[nitrogen]] in the process of biological [[nitrogen fixation]]. At least 50 molybdenum enzymes are now known in bacteria, plants, and animals, although only bacterial and cyanobacterial enzymes are involved in nitrogen fixation. Most [[nitrogenase]]s contain an iron–molybdenum cofactor [[FeMoco]], which is believed to contain either Mo(III) or Mo(IV).<ref>{{Cite journal |last1=Bjornsson |first1=Ragnar |last2=Neese |first2=Frank |last3=Schrock |first3=Richard R. |last4=Einsle |first4=Oliver |last5=DeBeer |first5=Serena |date=2015 |title=The discovery of Mo(III) in FeMoco: reuniting enzyme and model chemistry |doi-access=free |journal=Journal of Biological Inorganic Chemistry |volume=20 |issue=2 |pages=447–460 |doi=10.1007/s00775-014-1230-6 |issn=0949-8257 |pmc=4334110 |pmid=25549604}}</ref><ref>{{Cite journal |last1=Van Stappen |first1=Casey |last2=Davydov |first2=Roman |last3=Yang |first3=Zhi-Yong |last4=Fan |first4=Ruixi |last5=Guo |first5=Yisong |last6=Bill |first6=Eckhard |last7=Seefeldt |first7=Lance C. |last8=Hoffman |first8=Brian M. |last9=DeBeer |first9=Serena |date=2019-09-16 |title=Spectroscopic Description of the E1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies |doi-access=free |journal=Inorganic Chemistry |volume=58 |issue=18 |pages=12365–12376 |doi=10.1021/acs.inorgchem.9b01951 |issn=0020-1669 |pmc=6751781 |pmid=31441651}}</ref> By contrast Mo(VI) and Mo(IV) are complexed with [[molybdopterin]] in all other molybdenum-bearing enzymes.<ref>{{Cite journal |last=Leimkühler |first=Silke |date=2020 |title=The biosynthesis of the molybdenum cofactors in Escherichia coli |bibcode-access=free |journal=Environmental Microbiology |language=en |volume=22 |issue=6 |pages=2007–2026 |doi=10.1111/1462-2920.15003|issn=1462-2920 |pmid=32239579 |bibcode=2020EnvMi..22.2007L |doi-access=free}}</ref> Molybdenum is an [[essential element]] for all higher [[eukaryote]] organisms, including humans. A species of [[sponge]], ''[[Theonellidae|Theonella conica]]'', is known for hyperaccumulation of molybdenum.<ref>{{Cite journal |last1=Shoham |first1=Shani |last2=Keren |first2=Ray |last3=Lavy |first3=Adi |last4=Polishchuk |first4=Iryna |last5=Pokroy |first5=Boaz |last6=Ilan |first6=Micha |date=2024-07-19 |title=Out of the blue: Hyperaccumulation of molybdenum in the Indo-Pacific sponge ''Theonella conica'' |url=http://dx.doi.org/10.1126/sciadv.adn3923 |journal=Science Advances |volume=10 |issue=29 |pages=eadn3923 |doi=10.1126/sciadv.adn3923 |issn=2375-2548 |pmc=466961 |pmid=39018411|bibcode=2024SciA...10N3923S }}</ref>

==Characteristics==

===Physical properties===
In its pure form, molybdenum is a silvery-grey metal with a [[Mohs scale of mineral hardness|Mohs hardness]] of 5.5 and a standard atomic weight of 95.95&nbsp;g/mol.<ref>{{cite journal |author1=Wieser, M. E. |author2=Berglund, M. |s2cid=98084907 |date=2009 |title=Atomic weights of the elements 2007 (IUPAC Technical Report) |url=http://www.ciaaw.org/pubs/TSAW2007.pdf |journal=[[Pure and Applied Chemistry]] |volume=81 |issue=11 |pages=2131–2156 |doi-access=free |s2cid-access=free |doi=10.1351/PAC-REP-09-08-03 |access-date=2012-02-13 |archive-url=https://web.archive.org/web/20120311194819/http://www.ciaaw.org/pubs/TSAW2007.pdf |archive-date=2012-03-11}}</ref><ref>{{cite web |url=http://www.ciaaw.org/atomic_weights3.htm |title=Current Table of Standard Atomic Weights in Alphabetical Order: Standard Atomic weights of the elements |date=2013 |last=Meija |first=Juris |display-authors=etal |publisher=Commission on Isotopic Abundances and Atomic Weights |archive-url=https://web.archive.org/web/20140429050401/http://www.ciaaw.org/atomic_weights3.htm |archive-date=2014-04-29 }}</ref> It has a [[melting point]] of {{convert|2623|°C|°F}}, sixth highest of the naturally occurring elements; only [[tantalum]], [[osmium]], [[rhenium]], [[tungsten]], and [[carbon]] have higher melting points.<ref name="CRCdescription2" /> It has one of the lowest coefficients of [[thermal expansion]] among commercially used metals.<ref name="nbb">{{cite book |last=Emsley |first=John |title=Nature's Building Blocks |url=https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA265 |publisher=Oxford University Press |date=2001 |location=Oxford |pages=262–266 |isbn=978-0-19-850341-5}}</ref>

===Chemical properties===
Molybdenum is a [[transition metal]] with an [[electronegativity]] of 2.16 on the [[Pauling scale]]. It does not visibly react with oxygen or water at room temperature, but is attacked by halogens and hydrogen peroxide. Weak oxidation of molybdenum starts at {{convert|300|°C|°F}}; bulk oxidation occurs at temperatures above 600&nbsp;°C, resulting in [[molybdenum trioxide]]. Like many heavier transition metals, molybdenum shows little inclination to form a cation in aqueous solution, although the Mo<sup>3+</sup> cation is known to form under carefully controlled conditions.<ref>{{cite book |last=Parish |first=R. V. |date=1977 |title=The Metallic Elements |url=https://archive.org/details/metallicelements0000pari|url-access=registration |location=New York |publisher=Longman |pages=[https://archive.org/details/metallicelements0000pari/page/112 112], 133 |isbn=978-0-582-44278-8 }}</ref>

Gaseous molybdenum consists of the diatomic species Mo<sub>2</sub>.  That molecule is a [[singlet state|singlet]], with two unpaired electrons in bonding orbitals, in addition to 5 conventional bonds.  The result is a [[sextuple bond]].<ref>{{cite journal|title = The Many Ways To Have a Quintuple Bond|first1= Gabriel|last1= Merino|first2= Kelling J.|last2= Donald|first3= Jason S.|last3= D’Acchioli|first4= Roald|last4= Hoffmann|journal = [[J. Am. Chem. Soc.]]|year = 2007|volume = 129|issue = 49|pages = 15295–15302|doi = 10.1021/ja075454b|pmid = 18004851}}</ref><ref name="Roos">{{cite journal|last1=Roos|first1=Björn O.|last2=Borin|first2=Antonio C.|author3=Laura Gagliardi|year=2007|title=Reaching the Maximum Multiplicity of the Covalent Chemical Bond|url=https://www.academia.edu/13598187|journal=[[Angew. Chem. Int. Ed.]]|volume=46|issue=9|pages=1469–1472|doi=10.1002/anie.200603600|pmid=17225237}}</ref>

===Isotopes===
{{Main|Isotopes of molybdenum}}
There are 39 known [[isotopes]] of molybdenum, ranging in [[atomic mass]] from 81 to 119, as well as 13 metastable [[nuclear isomer]]s. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, only molybdenum-100 is unstable.{{NUBASE2020|ref}}

Molybdenum-98 is the most [[isotopic abundance|abundant]] isotope, comprising 24.14% of all molybdenum. Molybdenum-100 has a [[half-life]] of about 10<sup>19</sup>&nbsp;[[year|y]] and undergoes [[double beta decay]] into ruthenium-100. All unstable isotopes of molybdenum decay into isotopes of [[niobium]], [[technetium]], and [[ruthenium]]. Of the [[synthetic radioisotope]]s, the most stable is <sup>93</sup>Mo, with a half-life of 4,839 years.<ref name="93Mo"/>

The most common isotopic molybdenum application involves [[molybdenum-99]], which is a [[fission product]]. It is a [[parent radioisotope]] to the short-lived gamma-emitting daughter radioisotope [[technetium-99m]], a [[nuclear isomer]] used in various imaging applications in medicine.<ref name="armstrong">{{cite magazine|author=Armstrong, John T.|url=http://pubs.acs.org/cen/80th/technetium.html|title=Technetium|magazine=Chemical & Engineering News|date=2003|access-date=2009-07-07|archive-url=https://web.archive.org/web/20081006002652/http://pubs.acs.org/cen/80th/technetium.html|archive-date=2008-10-06|url-status=live}}</ref>
In 2008, the [[Delft University of Technology]] applied for a patent on the molybdenum-98-based production of molybdenum-99.<ref>Wolterbeek, Hubert Theodoor; Bode, Peter [https://archive.today/20130122082910/http://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&adjacent=true&locale=nl_NL&FT=D&date=20110330&CC=EP&NR=2301041A1&KC=A1 "A process for the production of no-carrier added 99Mo"]. European Patent EP2301041 (A1) ― 2011-03-30. Retrieved on 2012-06-27.</ref>

==Compounds==
{{Category see also|Molybdenum compounds}}
Molybdenum forms chemical compounds in oxidation states −4 and from −2 to +6. Higher oxidation states are more relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with [[metal cluster]]s, and very low oxidation states are typically associated with [[organomolybdenum compound]]s. The chemistry of molybdenum and tungsten show strong similarities. The relative rarity of molybdenum(III), for example, contrasts with the pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in [[molybdenum(VI) oxide]] (MoO<sub>3</sub>), whereas the normal sulfur compound is [[molybdenum disulfide]] MoS<sub>2</sub>.<ref name="Holl" />

{|class="wikitable" style="float:left; margin-right: 1em;"
|-
!Oxidation <br />state
!Example<ref name="Schmidt">{{Cite book |last=Hofmann |first=Karl A. |chapter-url=https://doi.org/10.1007/978-3-663-14240-9_31 |title=Anorganische Chemie |date=1973 |publisher=Vieweg+Teubner Verlag |isbn=978-3-663-14240-9 |editor-last=Hofmann |editor-first=Karl A. |location=Wiesbaden |pages=627–641 |language=de |chapter=VI. Nebengruppe |doi=10.1007/978-3-663-14240-9_31 |editor-last2=Hofmann |editor-first2=Ulrich |editor-last3=Rüdorff |editor-first3=Walter}}</ref><ref name="auto">{{Cite book |last=Werner |first=Helmut |url=https://books.google.com/books?id=dP4LTfaPzAMC |title=Landmarks in Organo-Transition Metal Chemistry: A Personal View |date=2008 |publisher=Springer Science & Business Media |isbn=978-0-387-09848-7 |language=en}}</ref>
|-
| −4||{{chem|Na|4|[Mo|(CO)|4|]}}
|-
| −2||{{chem|[Mo|(CO)|5|]|2-}}<ref>{{Cite journal
 | title = Metal Carbonyl Anions: from [Fe(CO)<sub>4</sub>]<sup>2−</sup> to [Hf(CO)<sub>6</sub>]<sup>2−</sup> and Beyond
 | author = Ellis, J. E.
 | journal = [[Organometallics]]
 | year = 2003 | volume = 22 | issue = 17 | pages = 3322–3338
 | doi = 10.1021/om030105l
}}</ref>
|-
| −1||{{chem|Na|2|[Mo|2|(CO)|10|]}}
|-
| 0||[[Molybdenum hexacarbonyl|{{chem|Mo(CO)|6|}}]]
|-
| +1||[[Cyclopentadienylmolybdenum tricarbonyl|{{chem|C|5|H|5|Mo(CO)|3}}]]
|-
| +2||[[Molybdenum(II) chloride|{{chem|MoCl|2}}]]
|-
| +3||[[Molybdenum(III) bromide|{{chem|MoBr|3}}]]
|-
| '''+4'''||[[Molybdenum disulfide|{{chem|MoS|2}}]]
|-
| +5||[[Molybdenum(V) chloride|{{chem|MoCl|5}}]]
|-
| '''+6'''||[[Molybdenum(VI) fluoride|{{chem|MoF|6}}]]
|}
[[File:Phosphotungstate-3D-polyhedra.png|thumb|upright|[[Keggin structure]] of the phosphomolybdate anion (P[Mo<sub>12</sub>O<sub>40</sub>]<sup>3−</sup>), an example of a [[polyoxometalate]]]]

From the perspective of commerce, the most important compounds are molybdenum disulfide ({{chem|MoS|2}}) and molybdenum trioxide ({{chem|MoO|3}}). The black disulfide is the main mineral. It is roasted in air to give the trioxide:<ref name="Holl" />

:2 {{chem|MoS|2}} + 7 {{chem|O|2}} → 2 {{chem|MoO|3}} + 4 {{chem|SO|2}}

The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has several [[oxidation state]]s, the most stable being +4 and +6 (bolded in the table at left).

Molybdenum(VI) oxide is soluble in strong [[base (chemistry)|alkaline]] water, forming molybdates (MoO<sub>4</sub><sup>2−</sup>). Molybdates are weaker oxidants than [[chromates]]. They tend to form structurally complex [[oxyanion]]s by condensation at lower [[pH]] values, such as [Mo<sub>7</sub>O<sub>24</sub>]<sup>6−</sup> and [Mo<sub>8</sub>O<sub>26</sub>]<sup>4−</sup>. Polymolybdates can incorporate other ions, forming [[polyoxometalate]]s.<ref>{{cite journal|journal = Angewandte Chemie International Edition|volume = 30|pages=34–48|date = 1997|title = Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines|first1 = Michael T.|last1 = Pope|last2= Müller |first2 = Achim|doi = 10.1002/anie.199100341}}</ref> The dark-blue [[phosphorus]]-containing heteropolymolybdate P[Mo<sub>12</sub>O<sub>40</sub>]<sup>3−</sup> is used for the [[ultraviolet-visible spectroscopy|spectroscopic]] detection of phosphorus.<ref>{{cite book|isbn = 978-0-8247-8433-1|pages = 280–288|editor = Nollet, Leo M. L.|date = 2000|publisher = Marcel Dekker|location = New York, NY|title = Handbook of water analysis|url=https://books.google.com/books?id=YZpW4Y4Q_PIC&pg=PA280}}</ref> 

The broad range of [[oxidation state]]s of molybdenum is reflected in various molybdenum chlorides:<ref name="Holl" />
* [[Molybdenum(II) chloride]] MoCl<sub>2</sub>, which exists as the hexamer Mo<sub>6</sub>Cl<sub>12</sub> and the related dianion [Mo<sub>6</sub>Cl<sub>14</sub>]<sup>2-</sup>.
* [[Molybdenum(III) chloride]] MoCl<sub>3</sub>, a dark red solid, which converts to the anion trianionic complex [MoCl<sub>6</sub>]<sup>3-</sup>.
* [[Molybdenum tetrachloride|Molybdenum(IV) chloride]] MoCl<sub>4</sub>, a black solid, which adopts a polymeric structure.
* [[Molybdenum(V) chloride]] MoCl<sub>5</sub> dark green solid, which adopts a dimeric structure.
* [[Molybdenum(VI) chloride]] MoCl<sub>6</sub> is a black solid, which is monomeric and slowly decomposes to MoCl<sub>5</sub> and Cl<sub>2</sub> at room temperature.<ref>{{Cite journal|last1=Tamadon|first1=Farhad|last2=Seppelt|first2=Konrad|date=2013-01-07|title=The Elusive Halides VCl 5, MoCl 6, and ReCl 6|journal=Angewandte Chemie International Edition|language=en|volume=52|issue=2|pages=767–769|doi=10.1002/anie.201207552|pmid=23172658}}</ref>

The accessibility of these oxidation states depends quite strongly on the halide counterion: although [[molybdenum(VI) fluoride]] is stable, molybdenum does not form a stable hexachloride, pentabromide, or tetraiodide.<ref>{{Kirk-Othmer|doi=10.1002/0471238961.1315122519200905.a01.pub3|title=Molybdenum Compounds|first=Edward&nbsp;I.|last=Stiefel}}</ref>  

Like [[chromium]] and some other transition metals, molybdenum forms [[quadruple bond]]s, such as in Mo<sub>2</sub>(CH<sub>3</sub>COO)<sub>4</sub> and [Mo<sub>2</sub>Cl<sub>8</sub>]<sup>4−</sup>.<ref name="Holl" /><ref>{{Cite book|title=Inorganic Syntheses: Volume 36 |last1=Walton |first1=Richard A. |last2=Fanwick |first2=Phillip E. |last3=Girolami |first3=Gregory S. |last4=Murillo |first4=Carlos A. |last5=Johnstone |first5=Erik V. |date=2014 |publisher=John Wiley & Sons |isbn=978-1118744994 |editor-last=Girolami |editor-first=Gregory S. |pages=78–81 |language=en |doi=10.1002/9781118744994.ch16 |editor-last2=Sattelberger |editor-first2=Alfred P.}}</ref> The [[ECW model|Lewis acid]] properties of the butyrate and perfluorobutyrate dimers, [[ECW model|Mo<sub>2</sub>(O<sub>2</sub>CR)<sub>4</sub>]] and Rh<sub>2</sub>(O<sub>2</sub>CR) <sub>4</sub>, have been reported.<ref>{{Cite journal |last1=Drago |first1=Russell S. |last2=Long |first2=John R. |last3=Cosmano |first3=Richard |date=1982-06-01 |title=Comparison of the coordination chemistry and inductive transfer through the metal-metal bond in adducts of dirhodium and dimolybdenum carboxylates |journal=Inorganic Chemistry |language=en |volume=21 |issue=6 |pages=2196–2202 |doi=10.1021/ic00136a013 |issn=0020-1669}}</ref>

The oxidation state 0 and lower are possible with carbon monoxide as ligand, such as in [[molybdenum hexacarbonyl]], Mo(CO)<sub>6</sub>.<ref name="Holl" /><ref name="auto"/>

==History==
[[Molybdenite]]—the principal ore from which molybdenum is now extracted—was previously known as molybdena. Molybdena was confused with and often utilized as though it were [[graphite]]. Like graphite, molybdenite can be used to blacken a surface or as a solid lubricant.<ref name="Lansdown1999">{{cite book |last1=Lansdown |first1=A. R. |title=Molybdenum disulphide lubrication |volume=35 |series=Tribology and Interface Engineering |publisher=Elsevier |date=1999 |isbn=978-0-444-50032-8}}</ref> Even when molybdena was distinguishable from graphite, it was still confused with the common [[lead]] ore PbS (now called [[galena]]); the name comes from [[Ancient Greek]] {{lang|grc|Μόλυβδος}} ''{{lang|grc-Latn|molybdos}}'', meaning ''lead''.<ref name="nbb" /> (The Greek word itself has been proposed as a [[loanword]] from [[Anatolian languages|Anatolian]] [[Luvian language|Luvian]] and [[Lydian language|Lydian]] languages).<ref name="melchert">{{cite web| author=Melchert, Craig| title=Greek mólybdos as a Loanword from Lydian| publisher=[[University of North Carolina]] at [[Chapel Hill, North Carolina|Chapel Hill]]| url=http://www.linguistics.ucla.edu/people/melchert/webpage/molybdos.pdf| access-date=2011-04-23| archive-url=https://web.archive.org/web/20131231000505/http://www.linguistics.ucla.edu/people/Melchert/webpage/molybdos.pdf| archive-date=2013-12-31| url-status=live}}</ref>

Although (reportedly) molybdenum was deliberately alloyed with steel in one 14th-century Japanese sword (mfd. {{Circa|1330}}), that art was never employed widely and was later lost.<ref>{{cite web |title=Molybdenum History |publisher=International Molybdenum Association |archive-url=https://web.archive.org/web/20130722102351/http://www.imoa.info/molybdenum/molydbenum_history.php |archive-date=2013-07-22 |url=http://www.imoa.info/molybdenum/molydbenum_history.php}}</ref><ref>{{cite book |title=Accidental use of molybdenum in old sword led to new alloy |url=https://books.google.com/books?id=yUpYAAAAMAAJ&q=Japanese+sword+molybdenum |publisher=American Iron and Steel Institute |date=1948}}</ref> In the West in 1754, [[Bengt Andersson Qvist]] examined a sample of molybdenite and determined that it did not contain lead and thus was not galena.<ref name="vanderkrogt">{{cite web |last=Van der Krogt |first=Peter |title=Molybdenum |work=Elementymology & Elements Multidict |date=2006-01-10 |url=http://elements.vanderkrogt.net/element.php?sym=Mo |access-date=2007-05-20 |archive-url=https://web.archive.org/web/20100123002743/http://elements.vanderkrogt.net/element.php?sym=Mo |archive-date=2010-01-23 |url-status=dead}}</ref>

By 1778 [[Sweden|Swedish]] chemist [[Carl Wilhelm Scheele]] stated firmly that molybdena was (indeed) neither galena nor graphite.<ref name="elemental">{{cite web|last = Gagnon|first = Steve|title = Molybdenum|publisher = Jefferson Science Associates, LLC|url = http://education.jlab.org/itselemental/ele042.html|access-date = 2007-05-06|archive-url = https://web.archive.org/web/20070426150528/http://education.jlab.org/itselemental/ele042.html|archive-date = 2007-04-26|url-status = dead}}</ref><ref>{{cite journal|author = Scheele, C. W. K.|title = Versuche mit Wasserbley; Molybdaena|journal = Svenska Vetensk. Academ. Handlingar|page=238|date = 1779|volume = 40|url = http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=PPN324352840_0040}}</ref> Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, named ''molybdenum'' for the mineral in which it resided, and from which it might be isolated. [[Peter Jacob Hjelm]] successfully isolated molybdenum using [[carbon]] and [[linseed oil]] in 1781.<ref name="nbb" /><ref>{{cite journal|author = Hjelm, P. J.|title = Versuche mit Molybdäna, und Reduction der selben Erde|journal = Svenska Vetensk. Academ. Handlingar|page = 268|date = 1788|volume = 49|url = http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=PPN324352840_0009_02_NS}}</ref>

For the next century, molybdenum had no industrial use. It was relatively scarce, the pure metal was difficult to extract, and the necessary techniques of metallurgy were immature.<ref name="Hoyt1921">{{cite book | last1 = Hoyt | first1 = Samuel Leslie | title = Metallography | volume = 2 | publisher = McGraw-Hill | date = 1921 }}</ref><ref name="Krupp1888">{{cite book | last1 = Krupp | first1 = Alfred | last2 = Wildberger | first2 = Andreas | title = The metallic alloys: A practical guide for the manufacture of all kinds of alloys, amalgams, and solders, used by metal-workers ... with an appendix on the coloring of alloys | publisher = H.C. Baird & Co. | date = 1888 | page = 60 }}</ref><ref name="'Gupta1992'">{{cite book | last1 = Gupta | first1 = C. K. | title = Extractive Metallurgy of Molybdenum | publisher = CRC Press | date = 1992 | isbn = 978-0-8493-4758-0}}</ref> Early molybdenum steel alloys showed great promise of increased hardness, but efforts to manufacture the alloys on a large scale were hampered with inconsistent results, a tendency toward brittleness, and recrystallization. In 1906, [[William D. Coolidge]] filed a patent for rendering molybdenum [[Ductility|ductile]], leading to applications as a heating element for high-temperature furnaces and as a support for tungsten-filament light bulbs; oxide formation and degradation require that molybdenum be physically sealed or held in an inert gas.<ref>{{cite book | url = https://books.google.com/books?id=ZVkZNyVI4toC&pg=PA117 | page = 117 | title = The Making of American Industrial Research: Science and Business at Ge and Bell, 1876–1926 | isbn = 978-0521522373 | last1 = Reich | first1 = Leonard S. | date = 2002-08-22 | publisher = Cambridge University Press | access-date = 2016-04-07 | archive-url = https://web.archive.org/web/20140709171645/http://books.google.com/books?id=ZVkZNyVI4toC&pg=PA117 | archive-date = 2014-07-09 | url-status = live }}</ref> In 1913, [[Frank E. Elmore]] developed a [[froth flotation process]] to recover [[molybdenite]] from ores; flotation remains the primary isolation process.<ref>{{cite book | url = https://books.google.com/books?id=HT4aAQAAIAAJ&q=Elmore+flotation+molybdenum+1913| page = 3 | title = Molybdenum deposits of Canada | last1 = Vokes | first1 = Frank Marcus | date = 1963}}</ref>

During [[World War I]], demand for molybdenum spiked; it was used both in [[Vehicle armor|armor plating]] and as a substitute for tungsten in [[high-speed steel]]s. Some British tanks were protected by 75&nbsp;mm (3&nbsp;in) [[mangalloy|manganese steel]] plating, but this proved to be ineffective. The manganese steel plates were replaced with much lighter {{Convert|25|mm|inch|1|abbr=on}} molybdenum steel plates allowing for higher speed, greater maneuverability, and better protection.<ref name="nbb" /> The Germans also used molybdenum-doped [[steel]] for heavy artillery, like in the super-heavy howitzer [[Big Bertha (howitzer)|Big Bertha]],<ref>[http://www.lenntech.com/periodic/elements/mo.htm Chemical properties of molibdenum – Health effects of molybdenum – Environmental effects of molybdenum] {{Webarchive|url=https://web.archive.org/web/20160120203530/http://www.lenntech.com/periodic/elements/mo.htm |date=2016-01-20}}. lenntech.com</ref> because traditional steel melts at the temperatures produced by the propellant of the [[ton|one ton]] shell.<ref>{{Cite book |last=Kean |first=Sam |title=The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements |date=2011-06-06 |publisher=Back Bay Books |isbn=978-0-316-05163-7 |edition=Illustrated |pages=88–89 |language=English}}</ref> After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. In [[World War II]], molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.<ref name="Millholland1941">{{cite journal | first = Ray | last = Millholland | title = Battle of the Billions: American industry mobilizes machines, materials, and men for a job as big as digging 40 Panama Canals in one year | date = August 1941 | journal = Popular Science | page = 61 | url = https://books.google.com/books?id=xScDAAAAMBAJ&pg=PA56 | access-date = 2016-04-07 | archive-url = https://web.archive.org/web/20140709161654/http://books.google.com/books?id=xScDAAAAMBAJ&pg=PA56 | archive-date = 2014-07-09 | url-status = live }}</ref>

==Occurrence and production==
[[File:Molly Hill molybdenite.JPG|thumb|alt=Lustrous, silvery, flat, hexagonal crystals in roughly parallel layers sit flowerlike on a rough, translucent crystalline piece of quartz.|[[Molybdenite]] on quartz]]
Molybdenum is the [[Abundance of elements in Earth's crust|54th most abundant element in the Earth's crust]] with an average of 1.5 parts per million and the 25th most abundant element in the oceans, with an average of 10&nbsp;parts per billion; it is the 42nd most abundant element in the Universe.<ref name="nbb" /><ref name="Nostrand">{{cite book|contribution = Molybdenum|date = 2005|title = Van Nostrand's Encyclopedia of Chemistry|pages = 1038–1040|place= New York|publisher = Wiley-Interscience|isbn=978-0-471-61525-5|editor= Considine, Glenn D.}}</ref> The Soviet [[Luna 24]] mission discovered a molybdenum-bearing grain (1 × 0.6&nbsp;μm) in a [[pyroxene]] fragment taken from [[Mare Crisium]] on the [[Moon]].<ref>{{cite journal|url=http://www.minsocam.org/msa/AmMin/TOC/Abstracts/2002_Abstracts/Jan02_Abstracts/Jambor_p181_02.pdf|title=New mineral names|journal=American Mineralogist|volume=87|page=181|date=2002|author=Jambor, J.L.|display-authors=etal|access-date=2007-04-09|archive-url=https://web.archive.org/web/20070710054017/http://www.minsocam.org/msa/AmMin/TOC/Abstracts/2002_Abstracts/Jan02_Abstracts/Jambor_p181_02.pdf|archive-date=2007-07-10|url-status=live}}</ref> The comparative rarity of molybdenum in the Earth's crust is offset by its concentration in a number of water-insoluble ores, often combined with sulfur in the same way as copper, with which it is often found. Though molybdenum is found in such [[mineral]]s as [[wulfenite]] (PbMoO<sub>4</sub>) and [[powellite]] (CaMoO<sub>4</sub>), the main commercial source is [[molybdenite]] (Mo[[sulfur|S]]<sub>2</sub>). Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining.<ref name="CRCdescription2" />

The world's production of molybdenum was 250,000 tonnes in 2011, the largest producers being China (94,000&nbsp;t), the United States (64,000&nbsp;t), Chile (38,000&nbsp;t), Peru (18,000&nbsp;t) and Mexico (12,000&nbsp;t). The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China (4.3&nbsp;Mt), the US (2.7&nbsp;Mt) and Chile (1.2&nbsp;Mt). By continent, 93% of world molybdenum production is about evenly shared between North America, South America (mainly in Chile), and China. Europe and the rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder.<ref name="USGS" />

[[File:Molybdenum world production.svg|thumb|World production trend]]

In molybdenite processing, the ore is first roasted in air at a temperature of {{convert|700|°C|°F}}. The process gives gaseous sulfur dioxide and the [[Molybdenum trioxide|molybdenum(VI) oxide]]:<ref name="Holl" />

:<chem>2MoS2 + 7O2 -> 2MoO3 + 4SO2</chem>

The resulting oxide is then usually extracted with aqueous ammonia to give ammonium molybdate:
:<chem>MoO3 + 2NH3 + H2O -> (NH4)2(MoO4)</chem>
Copper, an impurity in molybdenite, is separated at this stage by treatment with [[hydrogen sulfide]].<ref name="Holl" /> Ammonium molybdate converts to [[ammonium dimolybdate]], which is isolated as a solid. Heating this solid gives molybdenum trioxide:<ref name="ullmann">{{cite book|doi=10.1002/14356007.a16_655|chapter=Molybdenum and Molybdenum Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Sebenik |first1=Roger F. |last2=Burkin |first2=A. Richard |last3=Dorfler |first3=Robert R. |last4=Laferty |first4=John M. |last5=Leichtfried |first5=Gerhard |last6=Meyer-Grünow |first6=Hartmut |last7=Mitchell |first7=Philip C. H. |last8=Vukasovich |first8=Mark S. |last9=Church |first9=Douglas A. |last10=Van Riper |first10=Gary G. |last11=Gilliland |first11=James C. |last12=Thielke |first12=Stanley A. |isbn=3527306730 |s2cid=98762721 }}</ref>
: <chem>(NH4)2Mo2O7 -> 2MoO3 + 2NH3 + H2O</chem>
Crude trioxide can be further purified by sublimation at {{convert|1100|°C|°F}}.

Metallic molybdenum is produced by reduction of the oxide with hydrogen:
:<chem>MoO3 + 3H2 -> Mo + 3H2O</chem>

The molybdenum for steel production is reduced by the [[aluminothermic reaction]] with addition of iron to produce [[ferromolybdenum]]. A common form of ferromolybdenum contains 60% molybdenum.<ref name="Holl">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|pages = 1096–1104|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|author=Holleman, Arnold F. |author2=Wiberg, Egon |author3=Wiberg, Nils}}</ref><ref>{{cite book|last = Gupta|first = C. K.|title = Extractive Metallurgy of Molybdenum|publisher = CRC Press|date= 1992|pages = 1–2|isbn = 978-0-8493-4758-0}}</ref>

Molybdenum had a value of approximately $30,000 per tonne as of August 2009. It maintained a price at or near $10,000 per tonne from 1997 through 2003, and reached a peak of $103,000 per tonne in June 2005.<ref>{{cite web|title = Dynamic Prices and Charts for Molybdenum|publisher = InfoMine Inc.|date = 2007|url = http://www.infomine.com/investment/charts.aspx?c=molybdenum&u=mt&submit1=Display+Chart&x=usd&r=15y#chart|access-date = 2007-05-07|archive-url = https://web.archive.org/web/20091008202153/http://www.infomine.com/investment/charts.aspx?c=molybdenum&u=mt&submit1=Display+Chart&x=usd&r=15y#chart|archive-date = 2009-10-08|url-status = live}}</ref> In 2008, the [[London Metal Exchange]] announced that molybdenum would be traded as a commodity.<ref>{{cite web |title=LME to launch minor metals contracts in H2 2009 |url=http://www.lme.com/6241.asp |date=2008-09-04 |publisher=London Metal Exchange |access-date=2009-07-28 |archive-url=https://web.archive.org/web/20120722014344/http://www.lme.com/6241.asp |archive-date=2012-07-22 }}</ref>

===Mining===
The [[Knaben]] mine in southern Norway, opened in 1885, was the first dedicated molybdenum mine. Closed in 1973 but reopened in 2007,<ref>{{cite journal |doi = 10.1016/S0375-6742(96)00069-6 |title = Dispersion of tailings in the Knabena—Kvina drainage basin, Norway, 1: Evaluation of overbank sediments as sampling medium for regional geochemical mapping |date = 1997 |last1 = Langedal |first1 = M. |journal = Journal of Geochemical Exploration |volume = 58 |pages= 157–172 |issue = 2–3|bibcode = 1997JCExp..58..157L }}</ref> it now produces {{Convert|100000|kg|ton|0}} of molybdenum disulfide per year. Large mines in Colorado (such as the [[Henderson molybdenum mine|Henderson mine]] and the [[Climax mine]])<ref>{{cite journal|first= Paul B. |last = Coffman |title = The Rise of a New Metal: The Growth and Success of the Climax Molybdenum Company |journal = The Journal of Business of the University of Chicago |page= 30|date = 1937 |volume = 10 |doi = 10.1086/232443}}</ref> and in British Columbia yield molybdenite as their primary product, while many [[porphyry copper]] deposits such as the [[Bingham Canyon Mine]] in Utah and the [[Chuquicamata]] mine in northern Chile produce molybdenum as a byproduct of copper-mining.

==Applications==

===Alloys===
[[File:Plate of Molybdenum Copper .jpg|thumb|A plate of molybdenum copper alloy]]
About 86% of molybdenum produced is used in [[metallurgy]], with the rest used in chemical applications. The estimated global use is structural steel 35%, [[stainless steel]] 25%, chemicals 14%, tool & high-speed steels 9%, [[cast iron]] 6%, molybdenum elemental metal 6%, and [[superalloy]]s 5%.<ref>{{cite web |url=http://www.lme.com/minormetals/6782.asp |archive-url=https://web.archive.org/web/20120310004452/http://www.lme.com/minormetals/6782.asp |archive-date=2012-03-10 |title=Molybdenum |work=Industry usage |publisher=London Metal Exchange}}</ref>

Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, and supports for filaments in [[light bulbs]].<ref name="nbb" /><ref name="azom" />

Most high-strength steel [[alloy]]s (for example, [[41xx steel]]s) contain 0.25% to 8% molybdenum.<ref name="CRCdescription2" /> Even in these small portions, more than 43,000 tonnes of molybdenum are used each year in [[stainless steel]]s, [[tool steel]]s, cast irons, and high-temperature [[superalloy]]s.<ref name="Nostrand" />

Molybdenum is also used in steel alloys for its high [[corrosion]] resistance and [[weldability]].<ref name="Nostrand" /><ref name="USGS">{{cite web|title = Molybdenum Statistics and Information|publisher = U.S. Geological Survey|date = 2007-05-10|url = http://minerals.usgs.gov/minerals/pubs/commodity/molybdenum/|access-date = 2007-05-10|archive-url = https://web.archive.org/web/20070519151353/http://minerals.usgs.gov/minerals/pubs/commodity/molybdenum/|archive-date = 2007-05-19|url-status = live}}</ref> Molybdenum contributes corrosion resistance to type-300 stainless steels (specifically type-316) and especially so in the so-called [[Austenitic|superaustenitic]] stainless steels (such as alloy [[AL-6XN]], 254SMO and 1925hMo). Molybdenum increases lattice strain, thus increasing the energy required to dissolve iron atoms from the surface.{{contradictory inline|date=September 2018}} Molybdenum is also used to enhance the corrosion resistance of ferritic (for example grade 444)<ref>(2023) Stainless Steel Grades and Properties. International Molybdenum Association. https://www.imoa.info/molybdenum-uses/molybdenum-grade-stainless-steels/steel-grades.php?m=1683978651&</ref> and martensitic (for example 1.4122 and 1.4418) stainless steels.{{citation needed|date=December 2014}}

Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten.<ref name="Nostrand" /> An example is the 'M' series of high-speed steels such as M2, M4 and M42 as substitution for the 'T' steel series, which contain tungsten. Molybdenum can also be used as a flame-resistant coating for other metals. Although its melting point is {{convert|2623|°C|°F|abbr=on}}, molybdenum rapidly oxidizes at temperatures above {{convert|760|°C|°F|abbr=on}} making it better-suited for use in vacuum environments.<ref name="azom">{{cite web|title=Molybdenum|publisher=AZoM.com Pty. Limited|date=2007|url=http://www.azom.com/article.aspx?ArticleID=616|access-date=2007-05-06|archive-url=https://web.archive.org/web/20110614171110/http://www.azom.com/article.aspx?ArticleID=616|archive-date=2011-06-14|url-status=dead}}</ref>

TZM (Mo (~99%), Ti (~0.5%), Zr (~0.08%) and some C) is a corrosion-resisting molybdenum superalloy that resists molten fluoride salts at temperatures above {{convert|1300|°C|°F|abbr=on}}. It has about twice the strength of pure Mo, and is more ductile and more weldable, yet in tests it resisted corrosion of a standard eutectic salt ([[FLiBe]]) and salt vapors used in [[molten salt reactor]]s for 1100 hours with so little corrosion that it was difficult to measure.<ref>{{cite book|last=Smallwood|first=Robert E.|title=ASTM special technical publication 849: Refractory metals and their industrial applications: a symposium|chapter-url=https://books.google.com/books?id=agaacIr25KcC&pg=PA9|date=1984|publisher=ASTM International|isbn=978-0803102033|page=9|chapter=TZM Moly Alloy}}</ref><ref>{{cite web|url = http://www.energyfromthorium.com/forum/download/file.php?id=805|title = Compatibility of Molybdenum-Base Alloy TZM, with LiF-BeF<sub>2</sub>-ThF<sub>4</sub>-UF<sub>4</sub>|publisher = Oak Ridge National Laboratory Report|access-date = 2010-09-02|date = December 1969|archive-url = https://web.archive.org/web/20110710192254/http://www.energyfromthorium.com/forum/download/file.php?id=805|archive-date = 2011-07-10|url-status = dead}}</ref> Due to its excellent mechanical properties under high temperature and high pressure, TZM alloys are extensively applied in the military industry.<ref>{{cite web |url=https://apps.dtic.mil/sti/pdfs/AD0618935.pdf |title=A protective coating system for a TZM alloy re-entry vehicle |website=US Army |last=Levy |first=M. |date=1965 |access-date=June 3, 2024}}</ref> It is used as the valve body of [[torpedo]] engines, [[Rocket engine nozzle|rocket nozzles]] and gas pipelines, where it can withstand extreme thermal and mechanical stresses.<ref>{{cite journal |last1=Yang |first1=Zhi |last2=Hu |first2=Ke |date=2018 |title=Diffusion bonding between TZM alloy and WRe alloy by spark plasma sintering |journal=Journal of Alloys and Compounds |volume=764 |pages=582–590 |doi=10.1016/j.jallcom.2018.06.111}}</ref><ref>{{cite patent |country=CN |status=patent |number=109590476B}}</ref>  It is also used as [[radiation]] shields in nuclear applications.<ref>{{cite web |url=https://www.samaterials.com/content/preparation-application-of-tzm-alloy.html |title=Preparation & Application of TZM Alloy |last=Trento |first=Chin |website=Stanford Advanced Materials |date=Dec 27, 2023 |access-date=June 3, 2024}}</ref>

Other molybdenum-based alloys that do not contain iron have only limited applications. For example, because of its resistance to molten zinc, both pure molybdenum and molybdenum-[[tungsten]] alloys (70%/30%) are used for piping, stirrers and pump impellers that come into contact with molten zinc.<ref>{{cite book|title =Tool and manufacturing engineers handbook|first = W. H.|last = Cubberly|author2=Bakerjian, Ramon|publisher = Society of Manufacturing Engineers|isbn = 978-0-87263-351-3|url = https://books.google.com/books?id=NRXnXmFRjWYC&pg=PT421|page = 421|date =1989}}</ref>

===Pure element applications===
* Molybdenum powder is used as a fertilizer for some plants, such as [[cauliflower]].<ref name="Nostrand" />
* Elemental molybdenum is used in NO, NO<sub>2</sub>, NO<sub>x</sub> analyzers in power plants for pollution controls. At {{convert|350|°C|°F|abbr=on}}, the element acts as a catalyst for NO<sub>2</sub>/NO<sub>x</sub> to form NO molecules for detection by infrared light.<ref>{{cite journal|doi = 10.1023/A:1010730821844|date = 2001|last1= Lal|first1 = S.|last2 = Patil|first2 = R. S.|s2cid = 20441999|journal = Environmental Monitoring and Assessment|volume = 68|pages= 37–50|pmid = 11336410|title = Monitoring of atmospheric behaviour of NO<sub>x</sub> from vehicular traffic|issue = 1| bibcode=2001EMnAs..68...37L }}</ref>
* Molybdenum anodes replace tungsten in certain low voltage X-ray sources for specialized uses such as [[mammography]].<ref>{{cite book|title=Physics of Medical X-Ray Imaging|chapter-url=http://ric.uthscsa.edu/personalpages/lancaster/DI-II_Chapters/DI_chap4.pdf|chapter=Ch. 4: Physical determinants of contrast|author=Lancaster, Jack L.|publisher=University of Texas Health Science Center|url-status=dead|archive-url=https://web.archive.org/web/20151010172937/http://ric.uthscsa.edu/personalpages/lancaster/DI-II_Chapters/DI_chap4.pdf|archive-date=2015-10-10}}</ref>
* The radioactive isotope [[molybdenum-99]] is used to generate [[technetium-99m]], used for medical imaging<ref>[[Theodore Gray|Gray, Theodore]] (2009). ''The Elements''. Black Dog & Leventhal. pp. 105–107. {{ISBN|1-57912-814-9}}.</ref> The isotope is handled and stored as the molybdate.<ref>{{cite journal|doi = 10.1146/annurev.me.20.020169.001023|pmid = 4894500|date = 1969|last1 = Gottschalk|first1 = A.|title = Technetium-99m in clinical nuclear medicine|volume = 20|pages = 131–40|journal = Annual Review of Medicine|issue=1}}</ref>

===Compound applications===
* [[Molybdenum disulfide]] (MoS<sub>2</sub>) is used as a solid [[lubricant]] and a high-pressure high-temperature (HPHT) anti-wear agent. It forms strong films on metallic surfaces and is a common additive to HPHT greases — in the event of a catastrophic grease failure, a thin layer of molybdenum prevents contact of the lubricated parts.<ref>{{cite journal|doi =10.1016/0043-1648(67)90187-1|title =Molybdenum disulfide as a lubricant: A review of the fundamental knowledge |date =1967|last1 =Winer|first1 =W.|journal =Wear|volume =10|pages=422–452|issue =6|hdl =2027.42/33266 |url =https://deepblue.lib.umich.edu/bitstream/2027.42/33266/1/0000658.pdf|hdl-access =free}}</ref>
* When combined with small amounts of cobalt, MoS<sub>2</sub> is also used as a catalyst in the [[hydrodesulfurization]] (HDS) of petroleum.  In the presence of hydrogen, this catalyst facilitates the removal of nitrogen and especially sulfur from the feedstock, which otherwise would poison downstream catalysts.  HDS is one of the largest scale applications of catalysis in industry.<ref>{{cite book| author =Topsøe, H. |author2=Clausen, B. S. |author3=Massoth, F. E. | title =Hydrotreating Catalysis, Science and Technology| publisher = Springer-Verlag| location= Berlin| date = 1996}}</ref>
* Molybdenum oxides are important catalysts for selective oxidation of organic compounds.  The production of the commodity chemicals [[acrylonitrile]] and [[formaldehyde]] relies on MoO<sub>''x''</sub>-based catalysts.<ref name="ullmann"/>
* [[Molybdenum disilicide]] (MoSi<sub>2</sub>) is an electrically conducting [[ceramic]] with primary use in [[heating element]]s operating at temperatures above 1500&nbsp;°C in air.<ref>{{cite book|url=https://books.google.com/books?id=FbMfaqSgOxsC&pg=PA141|page=141|title=Electroceramics: materials, properties, applications|author=Moulson, A. J. |author2=Herbert, J. M.|publisher=John Wiley and Sons|date=2003|isbn=978-0-471-49748-6}}</ref>
* [[Molybdenum trioxide]] (MoO<sub>3</sub>) is used as an adhesive between [[Vitreous enamel|enamels]] and metals.<ref name="elemental" />
* [[Lead molybdate]] (wulfenite) co-precipitated with lead chromate and lead sulfate is a bright-orange pigment used with ceramics and plastics.<ref>[http://www.imoa.info/ International Molybdenum Association] {{Webarchive|url=https://web.archive.org/web/20080309010036/http://www.imoa.info/ |date=2008-03-09 }}. imoa.info.</ref>
* The molybdenum-based mixed oxides are versatile catalysts in the chemical industry. Some examples are the catalysts for the oxidation of carbon monoxide, propylene to [[acrolein]] and acrylic acid, the [[ammoxidation]] of propylene to acrylonitrile.<ref>{{cite book|editor=Fierro, J. G. L. |title=Metal Oxides, Chemistry and Applications|date=2006|publisher=CRC Press|pages=414–455}}</ref><ref>{{cite book|author1=Centi, G. |author2=Cavani, F. |author3=Trifiro, F. |title=Selective Oxidation by Heterogeneous Catalysis|date=2001|publisher=Kluwer Academic/Plenum Publishers|pages=363–384}}</ref>
* Molybdenum carbides, nitride and phosphides can be used for hydrotreatment of rapeseed oil.<ref>{{cite journal |last1=Horáček |first1=Jan |last2=Akhmetzyanova |first2=Uliana |last3=Skuhrovcová |first3=Lenka |last4=Tišler |first4=Zdeněk |last5=de Paz Carmona |first5=Héctor |title=Alumina-supported MoNx, MoCx and MoPx catalysts for the hydrotreatment of rapeseed oil |journal=Applied Catalysis B: Environmental |date=1 April 2020 |volume=263 |pages=118328 |doi=10.1016/j.apcatb.2019.118328 |s2cid=208758175 |language=en |issn=0926-3373|doi-access=free |bibcode=2020AppCB.26318328H }}</ref>
* [[Ammonium heptamolybdate]] is used in biological staining.<ref>{{cite journal |last1=De Carlo |first1=Sacha |last2=Harris |first2=J. Robin |title=Negative staining and cryo-negative staining of macromolecules and viruses for TEM |journal=Micron |volume=42 |date=2011 |issue=2 |pmid=20634082 |pmc=2978762 |doi=10.1016/j.micron.2010.06.003 |pages=117–131}}</ref>
* Molybdenum coated soda lime glass is used in CIGS ([[copper indium gallium selenide]]) [[solar cell]]s, called [[Copper indium gallium selenide solar cells|CIGS solar cells]].
* [[Phosphomolybdic acid]] is a stain used in [[thin-layer chromatography]]<ref>{{cite web | title = Stains for Developing TLC Plates | url = https://www.chemistry.mcmaster.ca/adronov/resources/Stains_for_Developing_TLC_Plates.pdf | publisher = McMaster University}}</ref> and [[Masson's trichrome|trichrome]] staining in [[histochemistry]].<ref>{{cite journal |last1= Everett |first1= M.M. |last2= Miller |first2= W.A. |date= 1974 |title= The role of phosphotungstic and phosphomolybdic acids in connective tissue staining I. Histochemical studies |journal= The Histochemical Journal |volume= 6 |issue= 1 |pages= 25–34 |doi= 10.1007/BF01011535|pmid= 4130630 }}</ref>

==Biological role==
{{Main|Molybdenum in biology}}
Molybdenum, despite its low concentration in the environment, is a critically important element for Earth's [[biosphere]] due to its presence in the most common [[nitrogenase]]s. Without molybdenum, [[nitrogen fixation]] would be greatly reduced, and a large part of [[biosynthesis]] as we know it would not occur. Molybdenum is also essential to many individual organisms as a component of enzymes, particularly as part of the [[molybdopterin]] class of [[Cofactor (biochemistry)|cofactor]]s.

===Mo-containing enzymes===
Molybdenum is an essential element in most organisms; a 2008 research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of [[eukaryote|eukaryotic life]] (which includes all plants and animals).<ref name="Scottetal">{{cite journal |last2=Lyons|first2=T. W. |last3=Bekker|first3=A.|last4=Shen|first4=Y. |last5=Poulton |first5=S. W. |last6=Chu |first6=X.|last7=Anbar|first7=A. D. |date=2008 |title=Tracing the stepwise oxygenation of the Proterozoic ocean |journal=Nature|volume=452|issue=7186 |pages=456–460 |bibcode=2008Natur.452..456S |doi=10.1038/nature06811 |pmid=18368114 |last1=Scott |first1=C.|s2cid=205212619 |doi-access= }}</ref>

At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria.<ref>{{cite journal |title=Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases |journal=Chem. Rev. |date=2004 |volume=104 |pages=1175–1200 |doi=10.1021/cr020609d |first1=John H. |last1=Enemark |first2=J. Jon A. |last2 =Cooney |first3=Jun-Jieh |last3=Wang |first4=R. H. |last4 =Holm |pmid=14871153 |issue=2}}</ref><ref>{{cite journal |doi=10.1016/j.bbamcr.2006.03.013 |pages=621–635 |pmid=16784786 |date=2006 |last1=Mendel |first1=Ralf R. |last2=Bittner |first2=Florian |title=Cell biology of molybdenum |journal=Biochimica et Biophysica Acta (BBA) - Molecular Cell Research |volume=1763 |issue=7}}</ref> Those enzymes include [[aldehyde oxidase]], [[sulfite oxidase]] and [[xanthine oxidase]].<ref name="nbb" /> With one exception, Mo in proteins is bound by [[molybdopterin]] to give the molybdenum cofactor. The only known exception is [[nitrogenase]], which uses the [[FeMoco]] cofactor, which has the formula Fe<sub>7</sub>MoS<sub>9</sub>C.<ref>{{cite journal |title=The Mononuclear Molybdenum Enzymes |author=Russ Hille |author2=James Hall |author3=Partha Basu|journal=Chem. Rev. |year=2014 |volume=114 |issue=7 |pages=3963–4038 |doi=10.1021/cr400443z |pmid=24467397 |pmc=4080432}}</ref>

In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating [[Nitrogen cycle|nitrogen]], [[Sulfur cycle|sulfur]], and [[carbon cycle|carbon]].<ref>{{cite journal |title=A structural comparison of molybdenum cofactor-containing enzymes |journal=FEMS Microbiol. Rev. |date=1999 |volume=22 |doi=10.1111/j.1574-6976.1998.tb00384.x |pmid=9990727 |issue=5 |pages=503–521 |last1=Kisker |first1=C. |last2=Schindelin |first2=H. |last3=Baas |first3=D. |last4=Rétey |first4=J. |last5=Meckenstock |first5=R. U. |last6=Kroneck |first6=P. M. H. |url=http://www.ioc.uni-karlsruhe.de/Professoren/Retey/fems_micro_reviews_1999_22_503.pdf |access-date=2017-10-25 |archive-url=https://web.archive.org/web/20170810025617/https://www.ioc.uni-karlsruhe.de/Professoren/Retey/fems_micro_reviews_1999_22_503.pdf |archive-date=2017-08-10 |url-status=live |doi-access=free}}</ref> In some animals, and in humans, the oxidation of [[xanthine]] to [[uric acid]], a process of [[purine]] [[catabolism]], is catalyzed by [[xanthine oxidase]], a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. An extremely high concentration of molybdenum reverses the trend and can inhibit purine catabolism and other processes. Molybdenum concentration also affects [[protein synthesis]], [[metabolism]], and growth.<ref name="IMOAoverview" />

Mo is a component in most [[nitrogenase]]s. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin.<ref>{{cite book
|first1=Ralf R. |last1=Mendel
|editor1-first=Lucia |editor1-last=Banci |series=Metal Ions in Life Sciences |volume=12
|chapter= Chapter 15 Metabolism of Molybdenum
|title=Metallomics and the Cell |date=2013 |publisher=Springer |isbn=978-94-007-5560-4
|doi=10.1007/978-94-007-5561-10_15 |doi-broken-date=1 November 2024
}} electronic-book {{ISBN|978-94-007-5561-1}} {{issn|1559-0836}} electronic-{{issn|1868-0402}}
</ref><ref>
{{cite book
|first1=Lee
|last1= Chi Chung
|first2=Ribbe
|last2= Markus W.
|first3=Hu
|last3= Yilin
|chapter= Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis and the First Step in Anaerobic Oxidation of the Greenhouse Gas Methane
|editor=Peter M.H. Kroneck
|editor2=Martha E. Sosa Torres
|title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment
|series=Metal Ions in Life Sciences
|volume=14
|date=2014
|publisher=Springer
|pages=147–174
|doi=10.1007/978-94-017-9269-1_6
|pmid= 25416393
|isbn= 978-94-017-9268-4
}}
</ref> Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:
:<math> \mathrm{N_2 + 8 \ H^+ + 8 \ e^- + 16 \ ATP + 16 \ H_2O \longrightarrow 2 \ NH_3 + H_2 + 16 \ ADP + 16 \ P_i} </math>
The [[biosynthesis]] of the [[FeMoco]] [[active site]] is highly complex.<ref>{{cite journal|title = A newly discovered role for iron-sulfur clusters|first1 = Patricia C.| doi = 10.1073/pnas.0805713105| journal=PNAS| date=2008|volume=105|pages=11589–11590 |pmid = 18697949| last1 = Dos Santos|last2 = Dean|first2 = Dennis R.|issue = 33|pmc = 2575256|bibcode = 2008PNAS..10511589D |doi-access = free}}</ref>
[[File:FeMoco cluster.svg|thumb|upright|Structure of the [[FeMoco]] active site of [[nitrogenase]]]]
[[File:Molybdenum cofactor.svg|thumb|upright=1.15|alt=Skeletal structure of a molybdopterin with a single molybdenum atom bound to both of the thiolate groups|The molybdenum cofactor (pictured) is composed of a molybdenum-free organic complex called [[molybdopterin]], which has bound an oxidized molybdenum(VI) atom through adjacent sulfur (or occasionally selenium) atoms. Except for the ancient nitrogenases, all known Mo-using enzymes use this cofactor.]]

Molybdate is transported in the body as MoO<sub>4</sub><sup>2−</sup>.<ref name="IMOAoverview">{{cite web |last=Mitchell |first=Phillip C. H. |title=Overview of Environment Database |publisher=International Molybdenum Association |date=2003 |url=http://hse.imoa.info/Default.asp?Page=110 |archive-url=https://web.archive.org/web/20071018005253/http://hse.imoa.info/Default.asp?Page=110 |archive-date=2007-10-18 |access-date=2007-05-05}}</ref>

===Human metabolism and deficiency===
Molybdenum is an essential trace [[dietary element]].<ref>{{cite book |first1= Guenter |last1= Schwarz |first2= Abdel A. |last2= Belaidi |chapter= Molybdenum in Human Health and Disease |editor=Astrid Sigel |editor2=Helmut Sigel |editor3=Roland K. O. Sigel |title=Interrelations between Essential Metal Ions and Human Diseases |series=Metal Ions in Life Sciences |volume=13 |date=2013 |publisher=Springer |pages=415–450 |doi=10.1007/978-94-007-7500-8_13|pmid= 24470099 |isbn= 978-94-007-7499-5 }}</ref> Four mammalian Mo-dependent enzymes are known, all of them harboring a [[pterin]]-based [[molybdopterin|molybdenum cofactor]] (Moco) in their active site: [[sulfite oxidase]], [[xanthine oxidase|xanthine oxidoreductase]], [[aldehyde oxidase]], and [[Mitochondrial amidoxime reducing component 1|mitochondrial amidoxime reductase]].<ref>{{cite journal| doi=10.1002/biof.55|title=Cell biology of molybdenum| date=2009| last1=Mendel| first1=Ralf R.| journal=BioFactors| volume=35| issue=5| pages=429–34| pmid=19623604|s2cid=205487570}}</ref> People severely deficient in molybdenum have poorly functioning sulfite oxidase and are prone to toxic reactions to sulfites in foods.<ref>''Blaylock Wellness Report'', February 2010, page 3.</ref><ref>{{cite journal| pmc=427300|title=Molecular Basis of the Biological Function of Molybdenum. The Relationship between Sulfite Oxidase and the Acute Toxicity of Bisulfite and SO<sub>2</sub>.| date=1973| last1=Cohen| first1=H. J.| last2=Drew| first2=R. T.| last3=Johnson| first3=J. L.| last4=Rajagopalan| first4=K. V.| volume=70| issue=12 Pt 1–2| pages=3655–3659| journal=Proceedings of the National Academy of Sciences of the United States of America|bibcode = 1973PNAS...70.3655C |doi = 10.1073/pnas.70.12.3655| pmid=4519654|doi-access=free}}</ref> The human body contains about 0.07&nbsp;mg of molybdenum per kilogram of body weight,<ref>{{cite book|date=2001|title=Inorganic chemistry|first1=Arnold F. |last1= Holleman|first2 = Egon|last2 = Wiberg|page=1384|url=https://books.google.com/books?id=vEwj1WZKThEC&pg=PA1384|publisher=Academic Press|isbn=978-0-12-352651-9}}</ref> with higher concentrations in the liver and kidneys and lower in the vertebrae.<ref name="Nostrand" /> Molybdenum is also present within human [[tooth enamel]] and may help prevent its decay.<ref>{{cite journal|title = Environmental Effects of Molybdenum on Caries|first1 = M. E. J.|last1 =Curzon|first2 = J.|last2 = Kubota| first3 = B. G.|last3 = Bibby|s2cid = 72386871|journal = Journal of Dental Research|volume = 50|issue =1|date = 1971|pages =74–77|doi = 10.1177/00220345710500013401}}</ref>

Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state. Studies on rats show a [[median lethal dose]] (LD<sub>50</sub>) as low as 180&nbsp;mg/kg for some Mo compounds.<ref name="ORNL">{{cite web|url = http://rais.ornl.gov/tox/profiles/molybdenum_f_V1.shtml|publisher=Oak Ridge National Laboratory|title=Risk Assessment Information System: Toxicity Summary for Molybdenum|access-date=2008-04-23 |archive-url = https://web.archive.org/web/20070919204536/http://rais.ornl.gov/tox/profiles/molybdenum_f_V1.shtml |archive-date = September 19, 2007}}</ref> Although human toxicity data is unavailable, animal studies have shown that chronic ingestion of more than 10&nbsp;mg/day of molybdenum can cause diarrhea, growth retardation, [[infertility]], low birth weight, and [[gout]]; it can also affect the lungs, kidneys, and liver.<ref name="Coug" /><ref>{{cite journal|doi = 10.1081/CLT-100102422|pages = 231–237|journal = Clinical Toxicology|date = 1999|volume = 37|issue =2|title = Molybdenum|first1 = Donald G.|last1 = Barceloux‌|first2 = Donald|last2 = Barceloux|pmid = 10382558}}</ref><!--Molybdenum deficiency is not usually seen in healthy people.<ref>{{cite web|title = Nutrient Reference Values for Australia|publisher = National Medical and Health Research Council (Australia)|url = http://www.nrv.gov.au/Nutrients.aspx?code=71128006|access-date = 2008-04-23}}</ref>--> [[Sodium tungstate]] is a [[competitive inhibition|competitive inhibitor]] of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.<ref name="Nostrand" />

Low soil concentration of molybdenum in a geographical band from northern China to Iran results in a general dietary [[molybdenum deficiency]] and is associated with increased rates of [[esophageal cancer]].<ref>{{cite journal|journal = Cancer Research|volume = 40|date = 1980|title = Research on Esophageal Cancer in China: a Review|first = Chung S.|last = Yang|url = http://cancerres.aacrjournals.org/content/40/8_Part_1/2633.full.pdf|pmid = 6992989|issue = 8 Pt 1|pages = 2633–44|access-date = 2011-12-30|archive-url = https://web.archive.org/web/20151123134413/http://cancerres.aacrjournals.org/content/40/8_Part_1/2633.full.pdf|archive-date = 2015-11-23|url-status = live}}</ref><ref>{{cite journal|journal = Archives of Iranian Medicine|date = 2008|volume = 11|title = Nail Molybdenum and Zinc Contents in Populations with Low and Moderate Incidence of Esophageal Cancer|first = Mohsen|last = Nouri|display-authors = 4|author2 = Chalian, Hamid|author3 = Bahman, Atiyeh|author4 = Mollahajian, Hamid|author5 = Ahmadi-Faghih, Mohammadamin|author6 = Fakheri, Hafez|author7 = Soroush, Ahmadreza|issue = 4|pages = 392–6|pmid = 18588371|url = http://www.ams.ac.ir/AIM/08114/0010.pdf|access-date = 2009-03-23|archive-url = https://web.archive.org/web/20110719080706/http://www.ams.ac.ir/AIM/08114/0010.pdf|archive-date = 2011-07-19|url-status = dead}}</ref><ref>{{cite journal |last1=Zheng |display-authors=etal |first1=Liu |title=Geographical distribution of trace elements-deficient soils in China |journal=Acta Ped. Sin. |date=1982 |volume=19 |pages=209–223 |url=http://en.cnki.com.cn/Article_en/CJFDTotal-TRXB198203000.htm |access-date=2020-07-25 |archive-date=2021-02-05 |archive-url=https://web.archive.org/web/20210205025802/http://en.cnki.com.cn/Article_en/CJFDTotal-TRXB198203000.htm |url-status=dead }}</ref> Compared to the United States, which has a greater supply of molybdenum in the soil, people living in those areas have about 16 times greater risk for [[Esophageal cancer|esophageal]] [[squamous cell carcinoma]].<ref>{{cite journal|url = http://cancerres.aacrjournals.org/content/canres/54/7_Supplement/2029s.full.pdf|journal = Cancer Research|volume = 54|pages = 2029s–2031s|date = 1994|title = Prevention of Esophageal Cancer: The Nutrition Intervention Trials in Linxian, China|first1 = Philip R.|last1 = Taylor|first2 = Bing|last2 = Li|first3 = Sanford M.|last3 = Dawsey|first4 = Jun-Yao|last4 = Li|first5 = Chung S.|last5 = Yang|first6 = Wande|last6 = Guo|first7 = William J.|last7 = Blot|pmid = 8137333|issue = 7 Suppl|access-date = 2016-07-01|archive-url = https://web.archive.org/web/20160917181412/http://cancerres.aacrjournals.org/content/canres/54/7_Supplement/2029s.full.pdf|archive-date = 2016-09-17|url-status = live}}</ref>

Molybdenum deficiency has also been reported as a consequence of non-molybdenum supplemented [[total parenteral nutrition]] (complete intravenous feeding) for long periods of time. It results in high blood levels of [[sulfite]] and [[urate]], in much the same way as [[molybdenum cofactor deficiency]]. Since pure molybdenum deficiency from this cause occurs primarily in adults, the neurological consequences are not as marked as in cases of congenital cofactor deficiency.<ref>{{cite journal|pmc=1911702|pmid=6426561|date=1984|author1-link=Naji Abumrad|last1=Abumrad|first1=N. N.|title=Molybdenum—is it an essential trace metal?|volume=60|issue=2|pages=163–71|journal=Bulletin of the New York Academy of Medicine}}</ref>

A congenital [[molybdenum cofactor deficiency]] disease, seen in infants, is an inability to synthesize [[molybdopterin|molybdenum cofactor]], the heterocyclic molecule discussed above that binds molybdenum at the active site in all known human enzymes that use molybdenum. The resulting deficiency results in high levels of [[sulfite]] and [[urate]], and neurological damage.<ref>{{cite journal|title=Splice-specific Functions of Gephyrin in Molybdenum Cofactor Biosynthesis|author=Smolinsky, B|journal=Journal of Biological Chemistry|doi=10.1074/jbc.M800985200|date=2008|volume=283|pages=17370–9|pmid=18411266|issue=25|last2=Eichler|first2=S. A.|last3=Buchmeier|first3=S.|last4=Meier|first4=J. C.|last5=Schwarz|first5=G.|doi-access=free}}</ref><ref>{{cite journal|doi = 10.1007/s004390051023|title=Genetics of molybdenum cofactor deficiency|date = 2000|last1 = Reiss|first1 = J.|journal = Human Genetics|volume = 106|pages = 157–63|pmid = 10746556|issue = 2|doi-broken-date=1 November 2024 }}</ref>

=== Excretion ===
Most molybdenum is excreted from the human body as molybdate in the urine. Furthermore, urinary excretion of molybdenum increases as dietary molybdenum intake increases. Small amounts of molybdenum are excreted from the body in the feces by way of the bile; small amounts also can be lost in sweat and in hair.<ref>{{Cite book|last1=Gropper|first1=Sareen S.|url=https://books.google.com/books?id=9-C5DQAAQBAJ|title=Advanced Nutrition and Human Metabolism|last2=Smith|first2=Jack L.|last3=Carr|first3=Timothy P.|date=2016-10-05|publisher=Cengage Learning|isbn=978-1-337-51421-7|language=en}}</ref><ref>{{Cite journal|last1=Turnlund|first1=J. R.|last2=Keyes|first2=W. R.|last3=Peiffer|first3=G. L.|date=October 1995|title=Molybdenum absorption, excretion, and retention studied with stable isotopes in young men at five intakes of dietary molybdenum|journal=The American Journal of Clinical Nutrition|volume=62|issue=4|pages=790–796|doi=10.1093/ajcn/62.4.790|issn=0002-9165|pmid=7572711|doi-access=free}}</ref>

===Excess and copper antagonism===
High levels of molybdenum can interfere with the body's uptake of [[copper]], producing [[copper deficiency]]. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted in [[urine]]. [[Ruminant]]s that consume high levels of molybdenum suffer from [[diarrhea]], stunted growth, [[anemia]], and [[Human hair color#Aging or achromotrichia|achromotrichia]] (loss of fur pigment). These symptoms can be alleviated by copper supplements, either dietary and injection.<ref name="suttle">{{cite journal|last = Suttle|first = N. F.|title = Recent studies of the copper-molybdenum antagonism|journal = Proceedings of the Nutrition Society|volume = 33|issue = 3|pages = 299–305|date= 1974|doi = 10.1079/PNS19740053|pmid = 4617883|doi-access = free}}</ref> The effective copper deficiency can be aggravated by excess [[sulfur]].<ref name="Nostrand" /><ref>Hauer, Gerald [http://www.bisoncentre.com/index.php?option=com_content&view=article&id=59&Itemid=256 Copper deficiency in cattle] {{Webarchive|url=https://web.archive.org/web/20110910172605/http://www.bisoncentre.com/index.php?option=com_content&view=article&id=59&Itemid=256 |date=2011-09-10 }}. Bison Producers of Alberta. Accessed Dec. 16, 2010.</ref>

Copper reduction or deficiency can also be deliberately induced for therapeutic purposes by the compound [[ammonium tetrathiomolybdate]], in which the bright red anion '''tetrathiomolybdate''' is the copper-chelating agent. Tetrathiomolybdate was first used therapeutically in the treatment of [[copper toxicosis]] in animals. It was then introduced as a treatment in [[Wilson's disease]], a hereditary copper metabolism disorder in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect on [[angiogenesis]], potentially by inhibiting the membrane translocation process that is dependent on copper ions.<ref>{{cite journal|author = Nickel, W|title = The Mystery of nonclassical protein secretion, a current view on cargo proteins and potential export routes|journal = [[Eur. J. Biochem.]]|date = 2003|volume = 270|pages = 2109–2119|doi = 10.1046/j.1432-1033.2003.03577.x|pmid=12752430|issue = 10|doi-access = free}}</ref> This is a promising avenue for investigation of treatments for [[cancer]], [[age-related macular degeneration]], and other diseases that involve a pathologic proliferation of blood vessels.<ref>{{cite journal|author=Brewer GJ|title=Treatment of Wilson disease with ammonium tetrathiomolybdate: III. Initial therapy in a total of 55 neurologically affected patients and follow-up with zinc therapy |journal=Arch Neurol |date=2003 |volume=60 |issue=3 |pages=379–85 |pmid=12633149 |doi=10.1001/archneur.60.3.379|last2=Hedera|first2=P.|last3=Kluin|first3=K. J.|last4=Carlson|first4=M.|last5=Askari|first5=F.|last6=Dick|first6=R. B.|last7=Sitterly|first7=J.|last8=Fink|first8=J. K.|doi-access=}}</ref><ref>{{cite journal|pmid=10656425|date=2000|last1=Brewer|first1=G. J.|last2=Dick|first2=R. D.|last3=Grover|first3=D. K.|last4=Leclaire|first4=V.|last5=Tseng|first5=M.|last6=Wicha|first6=M.|last7=Pienta|first7=K.|last8=Redman|first8=B. G.|last9=Jahan|first9=T.|last10=Sondak |first10=V. K.|last11=Strawderman |first11=M.|last12=LeCarpentier |first12=G.|last13=Merajver |first13=S. D.| title=Treatment of metastatic cancer with tetrathiomolybdate, an anticopper, antiangiogenic agent: Phase I study|volume=6|issue=1|pages=1–10|journal=Clinical Cancer Research}}</ref>

In some grazing livestock, most strongly in cattle, molybdenum excess in the soil of pasturage can produce scours ([[diarrhea]]) if the pH of the soil is neutral to alkaline; see [[wikt:teart#English|teartness]].

===Mammography===
Molybdenum targets are used in mammography because they produce X-rays in the energy range of 17-20 keV, which is optimal for imaging soft tissues like the breast.<ref>{{cite web |url=https://www.sputtertargets.net/blog/why-is-molybdenum-used-in-mammography-for-breast-cancer.html |title=Why is Molybdenum Target Used in Mammography for Breast Cancer? |last=Green |first=Julissa |website=Sputter Targets |access-date=Aug 2, 2024}}</ref><ref>{{cite book |year=2016 |title=IARC Working Group on the Evaluation of Cancer-Preventive Interventions: Breast cancer screening |publisher=Lyon (FR): International Agency for Research on Cancer |chapter=2. Screening Techniques |url=https://www.ncbi.nlm.nih.gov/books/NBK546557/ |access-date=Sep 2, 2024}}</ref> The characteristic X-rays emitted from molybdenum provide high contrast between different types of tissues, allowing for the effective visualization of microcalcifications and other subtle abnormalities in breast tissue.<ref>{{cite journal |first1=Qi-Hang |last1=Su |first2=Yan |last2=Zhang |year=2020 |title=Application of molybdenum target X-ray photography in imaging analysis of caudal intervertebral disc degeneration in rats |journal=World J Clin Cases |volume=8 |issue=6 |pages=3431–3439 |doi=10.12998/wjcc.v8.i16.3431 |doi-access=free |pmc=7457105 |pmid=32913849}}</ref> This energy range also minimizes radiation dose while maximizing image quality, making molybdenum targets particularly suitable for breast cancer screening.<ref>{{cite journal |first1=Khaled |last1=Alkhalifah |first2=Akram |last2=Asbeutah |year=2020 |title=Image Quality and Radiation Dose for Fibrofatty Breast using Target/filter Combinations in Two Digital Mammography Systems |journal=J Clin Imaging Sci |volume=10 |issue=56 |page=56 |doi=10.25259/JCIS_30_2020 |pmc=7533093 |pmid=33024611}}</ref>

==Dietary recommendations==
In 2000, the then U.S. Institute of Medicine (now the [[National Academy of Medicine]], NAM) updated its Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for molybdenum. If there is not sufficient information to establish EARs and RDAs, an estimate designated [[Adequate Intake]] (AI) is used instead.

An AI of 2&nbsp;[[microgram]]s (μg) of molybdenum per day was established for infants up to 6&nbsp;months of age, and 3&nbsp;μg/day from 7 to 12&nbsp;months of age, both for males and females. For older children and adults, the following daily RDAs have been established for molybdenum: 17&nbsp;μg from 1 to 3&nbsp;years of age, 22&nbsp;μg from 4 to 8&nbsp;years, 34&nbsp;μg from 9 to 13&nbsp;years, 43&nbsp;μg from 14 to 18 years, and 45&nbsp;μg for persons 19 years old and older. All these RDAs are valid for both sexes. [[Pregnancy|Pregnant]] or [[Breastfeeding|lactating]] females from 14 to 50&nbsp;years of age have a higher daily RDA of 50&nbsp;μg of molybdenum.

As for safety, the NAM sets [[tolerable upper intake level]]s (ULs) for vitamins and minerals when evidence is sufficient. In the case of molybdenum, the UL is 2000&nbsp;μg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as [[Dietary Reference Intake]]s (DRIs).<ref>{{cite book | last1 = Institute of Medicine | s2cid = 44243659 | title = Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc | chapter = Molybdenum | publisher = The National Academies Press | year = 2000 | location = Washington, DC | pages = 420–441 | chapter-url = https://www.nap.edu/read/10026/chapter/13| doi = 10.17226/10026 | pmid = 25057538 | isbn = 978-0-309-07279-3 | author1-link = Institute of Medicine }}</ref>

The [[European Food Safety Authority]] (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For women and men ages 15 and older, the AI is set at 65&nbsp;μg/day. Pregnant and lactating women have the same AI. For children aged 1–14&nbsp;years, the AIs increase with age from 15 to 45&nbsp;μg/day. The adult AIs are higher than the U.S. RDAs,<ref>{{cite web| title = Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies| year = 2017| url = https://www.efsa.europa.eu/sites/default/files/assets/DRV_Summary_tables_jan_17.pdf| access-date = 2017-09-10| archive-url = https://web.archive.org/web/20170828082247/https://www.efsa.europa.eu/sites/default/files/assets/DRV_Summary_tables_jan_17.pdf| archive-date = 2017-08-28| url-status = dead}}</ref> but on the other hand, the European Food Safety Authority reviewed the same safety question and set its UL at 600&nbsp;μg/day, which is much lower than the U.S. value.<ref>{{citation| title = Tolerable Upper Intake Levels For Vitamins And Minerals| publisher = European Food Safety Authority| year = 2006| url = http://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf| access-date = 2017-09-10| archive-url = https://web.archive.org/web/20160316225123/http://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf| archive-date = 2016-03-16| url-status = dead}}</ref>

===Labeling===
For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For molybdenum labeling purposes, 100% of the Daily Value was 75&nbsp;μg, but as of May 27, 2016 it was revised to 45&nbsp;μg.<ref name="FedReg">{{cite web |url=https://www.gpo.gov/fdsys/pkg/FR-2016-05-27/pdf/2016-11867.pdf |title=Federal Register May 27, 2016 Food Labeling: Revision of the Nutrition and Supplement Facts Labels. FR page 33982. |access-date=September 10, 2017 |archive-url=https://web.archive.org/web/20160808164651/https://www.gpo.gov/fdsys/pkg/FR-2016-05-27/pdf/2016-11867.pdf |archive-date=August 8, 2016 |url-status=live }}</ref><ref>{{cite web | title=Daily Value Reference of the Dietary Supplement Label Database (DSLD) | website=Dietary Supplement Label Database (DSLD) | url=https://www.dsld.nlm.nih.gov/dsld/dailyvalue.jsp | access-date=16 May 2020 | archive-date=7 April 2020 | archive-url=https://web.archive.org/web/20200407073956/https://dsld.nlm.nih.gov/dsld/dailyvalue.jsp | url-status=dead }}</ref> A table of the old and new adult daily values is provided at [[Reference Daily Intake]].

==Food sources==
Average daily intake varies between 120 and 240&nbsp;μg/day, which is higher than dietary recommendations.<ref name="Coug">{{cite journal|doi=10.1007/BF01811327|title=The role of molybdenum in human biology|date=1983|last=Coughlan|first = M. P.|s2cid=10114173|journal=Journal of Inherited Metabolic Disease|volume=6|pages=70–77|pmid=6312191|issue=S1}}</ref> Pork, lamb, and beef [[liver]] each have approximately 1.5 parts per million of molybdenum. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers, and cereal grain.<ref name="nbb" />

==Precautions==
Molybdenum dusts and fumes, generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in the [[paranasal sinuses|sinuses]] and later swallowed).<ref name="ORNL" /> Low levels of prolonged exposure can cause irritation to the eyes and skin. Direct inhalation or ingestion of molybdenum and its oxides should be avoided.<ref>{{cite web|title = Material Safety Data Sheet – Molybdenum|publisher = The REMBAR Company, Inc.|date= 2000-09-19|url = http://www.rembar.com/MSDSmo.htm|access-date = 2007-05-13 |archive-url = https://web.archive.org/web/20070323103727/http://www.rembar.com/MSDSmo.htm |archive-date = March 23, 2007}}</ref><ref>{{cite web|title = Material Safety Data Sheet – Molybdenum Powder|publisher = CERAC, Inc.|date= 1994-02-23|url = http://asp.cerac.com/CatalogNet/default.aspx?p=msdsFile&msds=m000121.htm|archive-url = https://web.archive.org/web/20110708132733/http://asp.cerac.com/CatalogNet/default.aspx?p=msdsFile&msds=m000121.htm|archive-date = 2011-07-08|access-date = 2007-10-19}}</ref> [[Occupational Safety and Health Administration|OSHA]] regulations specify the maximum permissible molybdenum exposure in an 8-hour day as 5&nbsp;mg/m<sup>3</sup>. Chronic exposure to 60&nbsp;to 600&nbsp;mg/m<sup>3</sup> can cause symptoms including fatigue, headaches and joint pains.<ref>{{cite web|title = NIOSH Documentation for IDLHs Molybdenum|publisher = National Institute for Occupational Safety and Health|date = 1996-08-16|url = https://www.cdc.gov/niosh/idlh/moly-mo.html|access-date = 2007-05-31|archive-url = https://web.archive.org/web/20070807130614/http://www.cdc.gov/niosh/idlh/moly-mo.html|archive-date = 2007-08-07|url-status = live}}</ref> At levels of 5000&nbsp;mg/m<sup>3</sup>, molybdenum is [[IDLH|immediately dangerous to life and health]].<ref>{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Molybdenum|url = https://www.cdc.gov/niosh/npg/npgd0433.html|website = www.cdc.gov|access-date = 2015-11-20|archive-url = https://web.archive.org/web/20151120130010/http://www.cdc.gov/niosh/npg/npgd0433.html|archive-date = 2015-11-20|url-status = live}}</ref>

==See also==
* [[List of molybdenum mines]]
* [[Molybdenum mining in the United States]]

==References==
{{Reflist|30em}}

== Bibliography ==
* {{Cite book |title=Lettera di Giulio Candida al signor Vincenzo Petagna – Sulla formazione del molibdeno |year=1785 |location=Naples |publisher=Giuseppe Maria Porcelli |url=https://archive.org/details/bub_gb_o_CjRnWqSNgC/page/n0 |ref=gcandida-molibdeno}}

==External links==
{{Commons|Molybdenum}}
{{Wiktionary|molybdenum}}
* [http://www.periodicvideos.com/videos/042.htm Molybdenum] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [http://www.mineral-exploration.com/publications.htm Mineral & Exploration] – Map of World Molybdenum Producers 2009
* [https://books.google.com/books?id=td4DAAAAMBAJ&pg=PA63 "Mining A Mountain" ''Popular Mechanics'', July 1935 pp. 63–64]
* [http://www.imoa.info/ Site for global molybdenum info]
* [https://www.cdc.gov/niosh/npg/npgd0433.html CDC – NIOSH Pocket Guide to Chemical Hazards]
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[[Category:Molybdenum| ]]
[[Category:Chemical elements]]
[[Category:Transition metals]]
[[Category:Refractory metals]]
[[Category:Dietary minerals]]
[[Category:Chemical elements with body-centered cubic structure]]
[[Category:Native element minerals]]