Editing Molybdenum (section)

==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>