Editing Fermium (section)

==Isotopes==
{{Main|Isotopes of fermium}}
[[File:Decay of Fermium-257.PNG|thumb|center|upright=3.5|Decay pathway of fermium-257]]
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There are 20 isotopes of fermium listed in N<small>UBASE</small>&nbsp;2016,{{NUBASE2016|ref}} with atomic weights of 241 to 260,{{efn|The discovery of {{sup|260}}Fm is considered "unproven" in N<small>UBASE</small>&nbsp;2003.<ref name="NUBASE2003">{{NUBASE 2003}}</ref>|name=Fm-260}} of which {{sup|257}}Fm is the longest-lived with a [[half-life]] of 100.5&nbsp;days. {{sup|253}}Fm has a half-life of 3 days, while {{sup|251}}Fm of 5.3&nbsp;h, {{sup|252}}Fm of 25.4&nbsp;h, {{sup|254}}Fm of 3.2&nbsp;h, {{sup|255}}Fm of 20.1&nbsp;h, and {{sup|256}}Fm of 2.6&nbsp;hours. All the remaining ones have half-lives ranging from 30 minutes to less than a millisecond.<ref name="NUBASE2003" />
The neutron capture product of fermium-257, {{sup|258}}Fm, undergoes [[spontaneous fission]] with a half-life of just 370(14)&nbsp;microseconds; {{sup|259}}Fm and {{sup|260}}Fm also undergo spontaneous fission (''t''<sub>1/2</sub>&nbsp;= 1.5(3)&nbsp;s and 4&nbsp;ms respectively).<ref name="NUBASE2003" /> This means that neutron capture cannot be used to create [[nuclide]]s with a [[mass number]] greater than 257, unless carried out in a nuclear explosion. As {{sup|257}}Fm [[alpha decay]]s to {{sup|253}}Cf, and no known fermium isotopes undergo [[beta minus decay]] to the next element, [[mendelevium]], fermium is also the last element that can be synthesized by neutron-capture.<ref name="Silva">{{cite book |last=Silva |first=Robert J. |chapter=Fermium, Mendelevium, Nobelium, and Lawrencium |title=The Chemistry of the Actinide and Transactinide Elements |editor1-first=Lester R. |editor1-last=Morss |editor2-first=Norman M. |editor2-last=Edelstein |editor3-first=Jean |editor3-last=Fuger |edition=3rd |date=2006 |volume=3 |publisher=Springer |location=Dordrecht |pages=1621–1651 |chapter-url=http://radchem.nevada.edu/classes/rdch710/files/Fm%20to%20Lr.pdf |doi=10.1007/1-4020-3598-5_13 |isbn=978-1-4020-3555-5 |archive-url=https://web.archive.org/web/20100717155410/http://radchem.nevada.edu/classes/rdch710/files/Fm%20to%20Lr.pdf |archive-date=2010-07-17}}</ref><ref name="G&E">{{Greenwood&Earnshaw1st|page=1262}}</ref><ref name="nuclidetable">{{cite web |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=100&n=147 |title=Interactive Chart of Nuclides |publisher=Brookhaven National Laboratory |author=Sonzogni, Alejandro |location=National Nuclear Data Center |access-date=2008-06-06 |archive-date=21 June 2018 |archive-url=https://web.archive.org/web/20180621170934/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=100&n=147 |url-status=dead }}</ref> Because of this impediment in forming heavier isotopes, these short-lived isotopes {{sup|258–260}}Fm constitute the "fermium gap."<ref name="Zagrebaev">{{cite journal|title=Future of superheavy element research: Which nuclei could be synthesized within the next few years?|url=http://nrv.jinr.ru/pdf_file/J_phys_2013.pdf|first1=Valeriy|last1=Zagrebaev|first2=Alexander|last2=Karpov|first3=Walter|last3=Greiner|date=2013|journal=Journal of Physics|volume=420|number=12001|page=11|doi=10.1088/1742-6596/420/1/012001|arxiv=1207.5700|bibcode=2013JPhCS.420a2001Z|s2cid=55434734}}</ref> 
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