View source for Physics:Isotopes of fermium

{{Short description|Nuclides with atomic number of 100 but with different mass numbers}}
{{infobox fermium isotopes}}
[[Chemistry:Fermium|Fermium]] (<sub>100</sub>Fm) is a [[Physics:Synthetic element|synthetic element]], and thus a [[Physics:Standard atomic weight|standard atomic weight]] cannot be given. Like all artificial elements, it has no [[Physics:Stable isotope|stable isotope]]s. The first [[Physics:Isotope|isotope]] to be discovered (in fallout from nuclear testing) was <sup>255</sup>Fm in 1952. <sup>250</sup>Fm was independently synthesized shortly after the discovery of <sup>255</sup>Fm. There are 20 known radioisotopes ranging in [[Physics:Atomic mass|atomic mass]] from <sup>241</sup>Fm to <sup>260</sup>Fm (<sup>260</sup>Fm is unconfirmed), and 4 [[Physics:Nuclear isomer|nuclear isomer]]s, <sup>247m</sup>Fm, <sup>250m</sup>Fm, <sup>251m</sup>Fm, and <sup>253m</sup>Fm. The longest-lived isotope is <sup>257</sup>Fm with a [[Physics:Half-life|half-life]] of 100.5 days, and the longest-lived isomer is <sup>247m</sup>Fm with a half-life of 5.1 seconds.

== List of isotopes ==
{{Isotopes table
|symbol=Fm
|refs=<!-- not NUBASE2016 yet (2019-07-14) -->
|notes=m, unc(), mass#, spin(), spin#, SF, EC, IT
}}
|-
| rowspan=2|<sup>241</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 141
| rowspan=2|241.07421(32)#
| rowspan=2|730(60)&nbsp;μs
| [[Physics:Spontaneous fission|SF]]
| (various)
| rowspan=2|5/2+#
|-
| [[Physics:Alpha decay|α]] (<14%)
| <sup>237</sup>Cf
|-
| <sup>242</sup>Fm
| style="text-align:right" | 100
| style="text-align:right" | 142
| 242.07343(43)#
| <4&nbsp;μs<ref name=":1">{{cite journal |last1=Khuyagbaatar |first1=J. |last2=Hofmann |first2=S. |last3=Heßberger |first3=F. P. |last4=Ackermann |first4=D. |last5=Burkhard |first5=H. G. |last6=Heinz |first6=S. |last7=Kindler |first7=B. |last8=Kojouharov |first8=I. |last9=Lommel |first9=B. |last10=Mann |first10=R. |last11=Maurer |first11=J. |last12=Nishio |first12=K. |last13=Novikov |first13=Yu. |title=Spontaneous fission of neutron-deficient fermium isotopes and the new nucleus 241Fm |journal=The European Physical Journal A |date=1 August 2008 |volume=37 |issue=2 |pages=177–183 |doi=10.1140/epja/i2008-10608-4 |bibcode=2008EPJA...37..177K |s2cid=18977014 |url=https://link.springer.com/content/pdf/10.1140/epja/i2008-10608-4.pdf |access-date=24 June 2023 |language=en |issn=1434-601X}}</ref>
| SF
| (various)
| 0+
|-
| rowspan=3|<sup>243</sup>Fm<ref name=":0">{{cite journal |last1=Khuyagbaatar |first1=J. |last2=Heßberger |first2=F. P. |last3=Hofmann |first3=S. |last4=Ackermann |first4=D. |last5=Burkhard |first5=H. G. |last6=Heinz |first6=S. |last7=Kindler |first7=B. |last8=Kojouharov |first8=I. |last9=Lommel |first9=B. |last10=Mann |first10=R. |last11=Maurer |first11=J. |last12=Nishio |first12=K. |title=α decay of Fm 243 143 and Fm 245 145 , and of their daughter nuclei |journal=Physical Review C |date=12 October 2020 |volume=102 |issue=4 |page=044312 |doi=10.1103/PhysRevC.102.044312 |s2cid=241259726 |url=https://journals.aps.org/prc/pdf/10.1103/PhysRevC.102.044312 |access-date=24 June 2023 |language=en |issn=2469-9985}}</ref>
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 143
| rowspan=3|243.07447(23)#
| rowspan=3|231(9)&nbsp;ms
| α (91%)
| <sup>239</sup>Cf
| rowspan=3|(7/2−)
|-
| SF (9%)
| (various)
|-
| [[Physics:Positron emission|β<sup>+</sup>]] (<10%)
| <sup>243</sup>Es
|-
| rowspan=2|<sup>244</sup>Fm<ref name=":1"/>
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 144
| rowspan=2|244.07404(22)#
| rowspan=2|3.12(8)&nbsp;ms
| SF
| (various)
| rowspan=2|0+
|-
| α (<1%)
| <sup>240</sup>Cf
|-
| rowspan=3|<sup>245</sup>Fm<ref>{{cite journal |last1=Tezekbayeva |first1=M. S. |last2=Yeremin |first2=A. V. |last3=Svirikhin |first3=A. I. |last4=Lopez-Martens |first4=A. |last5=Chelnokov |first5=M. L. |last6=Chepigin |first6=V. I. |last7=Isaev |first7=A. V. |last8=Izosimov |first8=I. N. |last9=Karpov |first9=A. V. |last10=Kuznetsova |first10=A. A. |last11=Malyshev |first11=O. N. |last12=Mukhin |first12=R. S. |last13=Popeko |first13=A. G. |last14=Popov |first14=Yu. A. |last15=Rachkov |first15=V. A. |last16=Sailaubekov |first16=B. S. |last17=Sokol |first17=E. A. |last18=Hauschild |first18=K. |last19=Jacob |first19=H. |last20=Chakma |first20=R. |last21=Dorvaux |first21=O. |last22=Forge |first22=M. |last23=Gall |first23=B. |last24=Kessaci |first24=K. |last25=Andel |first25=B. |last26=Antalic |first26=S. |last27=Bronis |first27=A. |last28=Mosat |first28=P. |title=Study of the production and decay properties of neutron-deficient nobelium isotopes |journal=The European Physical Journal A |date=24 March 2022 |volume=58 |issue=3 |pages=52 |doi=10.1140/epja/s10050-022-00707-9 |arxiv=2203.15659 |bibcode=2022EPJA...58...52T |s2cid=247720708 |url=https://link.springer.com/article/10.1140/epja/s10050-022-00707-9 |access-date=24 June 2023 |language=en |issn=1434-601X}}</ref>
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 145
| rowspan=3|245.07535(21)#
| rowspan=3|5.5(7)&nbsp;s
| α (88.5%)
| <sup>241</sup>Cf
| rowspan=3|(1/2+)
|-
| β<sup>+</sup> (11.5%)
| <sup>245</sup>Es
|-
| SF (<0.3%)<ref name=":0"/>
| (various)
|-
| rowspan=3|<sup>246</sup>Fm<ref>{{cite journal |last1=Venhart |first1=M. |last2=Heßberger |first2=F. P. |last3=Ackermann |first3=D. |last4=Antalic |first4=S. |last5=Gray-Jones |first5=C. |last6=Greenlees |first6=P. T. |last7=Heinz |first7=S. |last8=Herzberg |first8=R. -D. |last9=Hofmann |first9=S. |last10=Ketelhut |first10=S. |last11=Kindler |first11=B. |last12=Kojouharov |first12=I. |last13=Leino |first13=M. |last14=Lommel |first14=B. |last15=Mann |first15=R. |last16=Papadakis |first16=P. |last17=Rostron |first17=D. |last18=Rudolph |first18=D. |last19=Šáro |first19=Š. |last20=Sulignano |first20=B. |title=Decay study of 246Fm at SHIP |journal=The European Physical Journal A |date=4 February 2011 |volume=47 |issue=2 |pages=20 |doi=10.1140/epja/i2011-11020-9 |bibcode=2011EPJA...47...20V |s2cid=119353521 |url=https://link.springer.com/content/pdf/10.1140/epja/i2011-11020-9.pdf |access-date=24 June 2023 |language=en |issn=1434-601X}}</ref>
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 146
| rowspan=3|246.075350(17)
| rowspan=3|1.54(4)&nbsp;s
| α (93.2%)
| <sup>242</sup>Cf
| rowspan=3|0+
|-
| SF (6.8%)
| (various)
|-
| β<sup>+</sup> (<1.3%)
| <sup>246</sup>Es
|-
| rowspan=2|<sup>247</sup>Fm<ref>{{cite journal |last1=Heßberger |first1=F. P. |last2=Hofmann |first2=S. |last3=Ackermann |first3=D. |last4=Antalic |first4=S. |last5=Kindler |first5=B. |last6=Kojouharov |first6=I. |last7=Kuusiniemi |first7=P. |last8=Leino |first8=M. |last9=Lommel |first9=B. |last10=Mann |first10=R. |last11=Nishio |first11=K. |last12=Popeko |first12=A. G. |last13=Sulignano |first13=B. |last14=Saro |first14=S. |last15=Streicher |first15=B. |last16=Venhart |first16=M. |last17=Yeremin |first17=A. V. |title=Alpha-gamma decay studies of 255Rf, 251No and 247Fm |journal=The European Physical Journal A - Hadrons and Nuclei |date=1 December 2006 |volume=30 |issue=3 |pages=561–569 |doi=10.1140/epja/i2006-10137-2 |bibcode=2006EPJA...30..561H |s2cid=123871572 |url=https://link.springer.com/content/pdf/10.1140/epja/i2006-10137-2.pdf |access-date=24 June 2023 |language=en |issn=1434-601X}}</ref>
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 147
| rowspan=2|247.07695(12)#
| rowspan=2|31(1)&nbsp;s
| α (64%)
| <sup>243</sup>Cf
| rowspan=2|(7/2+)
|-
| β<sup>+</sup> (36%)
| <sup>247</sup>Es
|-
| rowspan=3  style="text-indent:1em" | <sup>247m</sup>Fm
| rowspan=3  colspan="3" style="text-indent:2em" | 45(7)&nbsp;keV
| rowspan=3| 5.1(2)&nbsp;s
| α (88%)
| <sup>243</sup>Cf
| rowspan=3|(1/2+)
|-
| IT (12%)
| <sup>247</sup>Fm
|-
| β<sup>+</sup>?
| <sup>247</sup>Es
|-
| rowspan=3|<sup>248</sup>Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 148
| rowspan=3|248.077186(9)
| rowspan=3|35.1(8)&nbsp;s
| α (93%)
| <sup>244</sup>Cf
| rowspan=3|0+
|-
| β<sup>+</sup> (7%)
| <sup>248</sup>Es
|-
| SF (.10%)
| (various)
|-
| rowspan=2|<sup>249</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 149
| rowspan=2|249.078928(7)
| rowspan=2|1.6(1)&nbsp;min
| β<sup>+</sup> (84.4%)
| <sup>249</sup>Es
| rowspan=2|(7/2+)
|-
| α (15.6%)<ref>{{cite journal |last1=Heßberger |first1=F. P. |last2=Antalic |first2=S. |last3=Ackermann |first3=D. |last4=Kalaninová |first4=Z. |last5=Heinz |first5=S. |last6=Hofmann |first6=S. |last7=Streicher |first7=B. |last8=Kindler |first8=B. |last9=Kojouharov |first9=I. |last10=Kuusiniemi |first10=P. |last11=Leino |first11=M. |last12=Lommel |first12=B. |last13=Mann |first13=R. |last14=Nishio |first14=K. |last15=Šáro |first15=Š. |last16=Sulignano |first16=B. |last17=Venhart |first17=M. |title=Alpha-gamma decay studies of 253No and its daughter products 253Md , 249Fm |journal=The European Physical Journal A |date=29 May 2012 |volume=48 |issue=5 |pages=75 |doi=10.1140/epja/i2012-12075-8 |bibcode=2012EPJA...48...75H |s2cid=254111959 |url=https://link.springer.com/content/pdf/10.1140/epja/i2012-12075-8.pdf |access-date=25 June 2023 |language=en |issn=1434-601X}}</ref>
| <sup>245</sup>Cf
|-
| rowspan=3|<sup>250</sup>Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 150
| rowspan=3|250.079521(9)
| rowspan=3|30.4(15)&nbsp;min
| α (90%)
| <sup>246</sup>Cf
| rowspan=3|0+
|-
| [[Physics:Electron capture|EC]] (10%)
| <sup>250</sup>Es
|-
| SF (6.9×10<sup>−3</sup>%)
| (various)
|-
| style="text-indent:1em" | <sup>250m</sup>Fm
| colspan="3" style="text-indent:2em" | 1199.2(10)&nbsp;keV
| 1.92(5)&nbsp;s
| IT
| <sup>250</sup>Fm
| (8−)
|-
| rowspan=2|<sup>251</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 151
| rowspan=2|251.081540(16)
| rowspan=2|5.30(8)&nbsp;h
| β<sup>+</sup> (98.2%)
| <sup>251</sup>Es
| rowspan=2|(9/2−)
|-
| α (1.8%)
| <sup>247</sup>Cf
|-
| style="text-indent:1em" | <sup>251m</sup>Fm
| colspan="3" style="text-indent:2em" | 200.09(11)&nbsp;keV
| 21.1(16)&nbsp;μs
| IT
| <sup>251</sup>Fm
| (5/2+)
|-
| rowspan=2|<sup>252</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 152
| rowspan=2|252.082467(6)
| rowspan=2|25.39(4)&nbsp;h
| α (99.99%){{r|g=n|r=Theoretically capable of β<sup>+</sup>β<sup>+</sup> decay to <sup>252</sup>Cf{{NUBASE2020|ref}}}}
| <sup>248</sup>Cf
| rowspan=2|0+
|-
| SF (.0023%)
| (various)
|-
| rowspan=2|<sup>253</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 153
| rowspan=2|253.085185(4)
| rowspan=2|3.00(12)&nbsp;d
| EC (88%)
| <sup>253</sup>Es
| rowspan=2|(1/2)+
|-
| α (12%)
| <sup>249</sup>Cf
|-
| style="text-indent:1em" | <sup>253m</sup>Fm<ref>{{cite journal |last1=Antalic |first1=S. |last2=Heßberger |first2=F. P. |last3=Ackermann |first3=D. |last4=Heinz |first4=S. |last5=Hofmann |first5=S. |last6=Kalaninová |first6=Z. |last7=Kindler |first7=B. |last8=Khuyagbaatar |first8=J. |last9=Kojouharov |first9=I. |last10=Kuusiniemi |first10=P. |last11=Leino |first11=M. |last12=Lommel |first12=B. |last13=Mann |first13=R. |last14=Nishio |first14=K. |last15=Šáro |first15=Š. |last16=Streicher |first16=B. |last17=Sulignano |first17=B. |last18=Venhart |first18=M. |title=Isomeric states in 253No and 253Fm |journal=The European Physical Journal A |date=20 May 2011 |volume=47 |issue=5 |pages=62 |doi=10.1140/epja/i2011-11062-y |bibcode=2011EPJA...47...62A |s2cid=121080273 |url=https://link.springer.com/content/pdf/10.1140/epja/i2011-11062-y.pdf |access-date=25 June 2023 |language=en |issn=1434-601X}}</ref>
| colspan="3" style="text-indent:2em" | ~351&nbsp;keV
| 0.56(6)&nbsp;μs
| IT
| <sup>253</sup>Fm
| (11/2-)
|-
| rowspan=2|<sup>254</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 154
| rowspan=2|254.0868544(30)
| rowspan=2|3.240(2)&nbsp;h
| α (99.94%)
| <sup>250</sup>Cf
| rowspan=2|0+
|-
| SF (.0592%)
| (various)
|-
| rowspan=2|<sup>255</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 155
| rowspan=2|255.089964(5)
| rowspan=2|20.07(7)&nbsp;h
| α
| <sup>251</sup>Cf
| rowspan=2|7/2+
|-
| SF (2.4×10<sup>−5</sup>%)
| (various)
|-
| rowspan=2|<sup>256</sup>Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 156
| rowspan=2|256.091774(8)
| rowspan=2|157.6(13)&nbsp;min
| SF (91.9%)
| (various)
| rowspan=2|0+
|-
| α (8.1%)
| <sup>252</sup>Cf
|-
| rowspan=2|<sup>257</sup>Fm<ref group="n">Heaviest nuclide produced via [[Physics:Neutron capture|neutron capture]]</ref>
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 157
| rowspan=2|257.095106(7)
| rowspan=2|100.5(2)&nbsp;d
| α (99.79%)
| <sup>253</sup>Cf
| rowspan=2|(9/2+)
|-
| SF (.21%)
| (various)
|-
| <sup>258</sup>Fm
| style="text-align:right" | 100
| style="text-align:right" | 158
| 258.09708(22)#
| 370(14)&nbsp;μs
| SF
| (various)
| 0+
|-
| <sup>259</sup>Fm
| style="text-align:right" | 100
| style="text-align:right" | 159
| 259.1006(3)#
| 1.5(3)&nbsp;s
| SF
| (various)
| 3/2+#
|-
| <sup>260</sup>Fm<ref group="n" name="uc">Discovery of this isotope is unconfirmed</ref><ref group="n">Not directly synthesized, occurs as decay product of <sup>260</sup>Md</ref>
| style="text-align:right" | 100
| style="text-align:right" | 160
| 260.10281(55)#
| 4&nbsp;ms
| SF
| (various)
| 0+
{{Isotopes table/footer}}

== Chronology of isotope discovery ==

{| class="wikitable"
! Isotope !! Discovered !! Reaction
|-
| <sup>241</sup>Fm || 2008|| <sup>204</sup>Pb(<sup>40</sup>Ar,3n)
|-
| <sup>242</sup>Fm || 1975|| <sup>204</sup>Pb(<sup>40</sup>Ar,2n), <sup>206</sup>Pb(<sup>40</sup>Ar,4n)
|-
| <sup>243</sup>Fm|| 1981|| <sup>206</sup>Pb(<sup>40</sup>Ar,3n)
|-
| <sup>244</sup>Fm|| 1967|| <sup>233</sup>U(<sup>16</sup>O,5n)
|-
| <sup>245</sup>Fm|| 1967|| <sup>233</sup>U(<sup>16</sup>O,4n)
|-
| <sup>246</sup>Fm|| 1966|| <sup>235</sup>U(<sup>16</sup>O,5n)
|-
| <sup>247</sup>Fm|| 1967|| <sup>239</sup>Pu(<sup>12</sup>C,4n)
|-
| <sup>248</sup>Fm|| 1958|| <sup>240</sup>Pu(<sup>12</sup>C,4n)
|-
| <sup>249</sup>Fm|| 1960|| <sup>238</sup>U(<sup>16</sup>O,5n)
|-
| <sup>250</sup>Fm|| 1954|| <sup>238</sup>U(<sup>16</sup>O,4n)
|-
| <sup>251</sup>Fm|| 1957|| <sup>249</sup>Cf(α,2n)
|-
| <sup>252</sup>Fm|| 1956|| <sup>249</sup>Cf(α,n)
|-
| <sup>253</sup>Fm|| 1957|| <sup>252</sup>Cf(α,3n)
|-
| <sup>254</sup>Fm|| 1954|| Neutron capture
|-
| <sup>255</sup>Fm|| 1954|| Neutron capture
|-
| <sup>256</sup>Fm|| 1955|| Neutron capture
|-
| <sup>257</sup>Fm|| 1964|| Neutron capture
|-
| <sup>258</sup>Fm|| 1971|| <sup>257</sup>Fm(d,p)
|-
| <sup>259</sup>Fm|| 1980|| <sup>257</sup>Fm(t,p)
|-
| <sup>260</sup>Fm?|| 1992?|| <sup>254</sup>Es+<sup>18</sup>O, <sup>22</sup>Ne — transfer (EC of <sup>260</sup>Md)
|}
<sup>260</sup>Fm was not confirmed in 1997.

== References ==
<references />
* Isotope masses from:
**{{cite journal |author=M. Wang |author2=G. Audi |author3=A. H. Wapstra |author4=F. G. Kondev |author5=M. MacCormick |author6=X. Xu|year=2012 |title=The AME2012 atomic mass evaluation (II). Tables, graphs and references. |url=http://amdc.in2p3.fr/masstables/Ame2012/Ame2012b-v2.pdf |journal=Chinese Physics C |volume=36 |issue= 12 |pages=1603–2014 |doi=10.1088/1674-1137/36/12/003|bibcode = 2012ChPhC..36....3M |s2cid=250839471 |display-authors=0}}
**{{NUBASE 2003}}
* Isotopic compositions and standard atomic masses from:
**{{CIAAW 2005}}
* Half-life, spin, and isomer data selected from the following sources.
**{{NUBASE 2012}}
**{{NUBASE 2003}}
**{{NNDC}}
**{{CRC85|chapter=11}}
**{{cite journal |author=M. Thoennessen |year=2012 |title=Discovery of Isotopes of Elements with Z≥100 |arxiv=1203.2105 |doi=10.1016/j.adt.2012.03.003 |volume=99 |issue=3 |journal=Atomic Data and Nuclear Data Tables |pages=312–344|bibcode=2013ADNDT..99..312T |s2cid=94982856 }}

{{Navbox element isotopes}}

[[Category:Isotopes of fermium| ]]
[[Category:Lists of isotopes by element|Fermium]]

{{Sourceattribution|Isotopes of fermium}}