Isotopes of fermium
Template:Short description Template:Infobox fermium isotopes Fermium (100Fm) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be discovered (in fallout from nuclear testing) was 255Fm in 1952. 250Fm was independently synthesized shortly after the discovery of 255Fm. There are 20 known radioisotopes ranging in atomic mass from 241Fm to 260Fm (260Fm is unconfirmed), and 4 nuclear isomers, 247mFm, 250mFm, 251mFm, and 253mFm. The longest-lived isotope is 257Fm with a half-life of 100.5 days, and the longest-lived isomer is 247mFm with a half-life of 5.1 seconds.
List of isotopes
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Template:Isotopes table
|-id=Fermium-241
| rowspan=3|241Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 141
| rowspan=3|241.07431(32)#
| rowspan=3|Script error: No such module "val".
| SF
| (various)
| rowspan=3|5/2+#
|-
| α (<14%)
| 237Cf
|-
| β+ (<12%)
| 241Es
|-id=Fermium-242
| 242Fm
| style="text-align:right" | 100
| style="text-align:right" | 142
| 242.07343(43)#
| Script error: No such module "val".
| SF
| (various)
| 0+
|-id=Fermium-243
| rowspan=2|243Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 143
| rowspan=2|243.07441(14)#
| rowspan=2|Script error: No such module "val".
| α (91%)
| 239Cf
| rowspan=2|7/2−#
|-
| SF (9%)
| (various)
|-id=Fermium-244
| rowspan=3|244Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 144
| rowspan=3|244.07404(22)#
| rowspan=3|Script error: No such module "val".
| SF (>97%)
| (various)
| rowspan=3|0+
|-
| β+ (<2%)
| 244Es
|-
| α (<1%)
| 240Cf
|-id=Fermium-245
| rowspan=3|245Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 145
| rowspan=3|245.07535(21)#
| rowspan=3|Script error: No such module "val".
| α (88.5%)
| 241Cf
| rowspan=3|1/2+#
|-
| β+ (11.5%)[1]
| 245Es
|-
| SF (<0.3%)
| (various)
|-id=Fermium-246
| rowspan=3|246Fm
| rowspan=3 style="text-align:right" | 100
| rowspan=3 style="text-align:right" | 146
| rowspan=3|246.075353(15)
| rowspan=3|Script error: No such module "val".
| α (93.2%)
| 242Cf
| rowspan=3|0+
|-
| SF (6.8%)
| (various)
|-
| EC (<1.3%)
| 246Es
|-id=Fermium-247
| rowspan=2|247Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 147
| rowspan=2|247.07694(19)#
| rowspan=2|Script error: No such module "val".
| α (~64%)
| 243Cf
| rowspan=2|(7/2+)
|-
| β+? (~36%)
| 247Es
|-id=Fermium-247m
| rowspan=2 style="text-indent:1em" | 247mFm
| rowspan=2 colspan="3" style="text-indent:2em" | 49(8) keV
| rowspan=2| Script error: No such module "val".
| α (88%)
| 243Cf
| rowspan=2|(1/2+)
|-
| IT? (12%)
| 247Fm
|-id=Fermium-248
| rowspan=2|248Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 148
| rowspan=2|248.077185(9)
| rowspan=2|Script error: No such module "val".
| α (99.9%)
| 244Cf
| rowspan=2|0+
|-
| SF (0.1%)
| (various)
|-id=Fermium-248m
| rowspan=3 style="text-indent:1em" | 248mFm
| rowspan=3 colspan="3" style="text-indent:2em" | 1200(100)# keV
| rowspan=3| Script error: No such module "val".
| IT?
| 248Fm
| rowspan=3|6+#
|-
| α?
| 244Cf
|-
| β+?
| 248Es
|-id=Fermium-249
| rowspan=2|249Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 149
| rowspan=2|249.078926(7)
| rowspan=2|Script error: No such module "val".
| β+? (67%)
| 249Es
| rowspan=2|7/2+
|-
| α (33%)
| 245Cf
|-id=Fermium-250
| rowspan=2|250Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 150
| rowspan=2|250.079520(8)
| rowspan=2|Script error: No such module "val".
| α (99.99%)
| 246Cf
| rowspan=2|0+
|-
| SF (6.9×10−3%)
| (various)
|-id=Fermium-250m
| style="text-indent:1em" | 250mFm
| colspan="3" style="text-indent:2em" | 1199.2(10) keV
| Script error: No such module "val".
| IT
| 250Fm
| (8−)
|-id=Fermium-251
| rowspan=2|251Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 151
| rowspan=2|251.081545(15)
| rowspan=2|Script error: No such module "val".
| β+ (98.20%)
| 251Es
| rowspan=2|9/2−
|-
| α (1.80%)
| 247Cf
|-id=Fermium-251m
| style="text-indent:1em" | 251mFm
| colspan="3" style="text-indent:2em" | 200.0(1) keV
| Script error: No such module "val".
| IT
| 251Fm
| 5/2+
|-id=Fermium-252
| rowspan=2|252Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 152
| rowspan=2|252.082466(6)
| rowspan=2|Script error: No such module "val".
| α (99.99%)Template:Refn
| 248Cf
| rowspan=2|0+
|-
| SF (0.0023%)
| (various)
|-id=Fermium-253
| rowspan=2|253Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 153
| rowspan=2|253.0851809(17)
| rowspan=2|Script error: No such module "val".
| EC (88%)
| 253Es
| rowspan=2|1/2+
|-
| α (12%)
| 249Cf
|-id=Fermium-253m
| style="text-indent:1em" | 253mFm
| colspan="3" style="text-indent:2em" | 351(6) keV
| Script error: No such module "val".
| IT
| 253Fm
| 11/2−#
|-id=Fermium-254
| rowspan=2|254Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 154
| rowspan=2|254.0868524(20)
| rowspan=2|Script error: No such module "val".
| α (99.94%)
| 250Cf
| rowspan=2|0+
|-
| SF (0.0592%)
| (various)
|-id=Fermium-255
| rowspan=2|255Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 155
| rowspan=2|255.089963(4)
| rowspan=2|Script error: No such module "val".
| α
| 251Cf
| rowspan=2|7/2+
|-
| SF (2.4×10−5%)
| (various)
|-id=Fermium-256
| rowspan=2|256Fm
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 156
| rowspan=2|256.091772(3)
| rowspan=2|Script error: No such module "val".
| SF (91.9%)
| (various)
| rowspan=2|0+
|-
| α (8.1%)
| 252Cf
|-id=Fermium-257
| rowspan=2|257Fm[n 1]
| rowspan=2 style="text-align:right" | 100
| rowspan=2 style="text-align:right" | 157
| rowspan=2|257.095105(5)
| rowspan=2|Script error: No such module "val".
| α (99.79%)
| 253Cf
| rowspan=2|9/2+
|-
| SF (0.210%)
| (various)
|-id=Fermium-258
| 258Fm
| style="text-align:right" | 100
| style="text-align:right" | 158
| 258.09708(22)#
| Script error: No such module "val".
| SF
| (various)
| 0+
|-id=Fermium-259
| 259Fm
| style="text-align:right" | 100
| style="text-align:right" | 159
| 259.10060(30)#
| Script error: No such module "val".
| SF
| (various)
|
|-id=Fermium-260
| 260Fm[n 2][n 3]
| style="text-align:right" | 100
| style="text-align:right" | 160
| 260.10281(47)#
| 1# min
| SF
| (various)
| 0+
Template:Isotopes table/footer
Chronology of isotope discovery
| Isotope | Discovered | Reaction |
|---|---|---|
| 241Fm | 2008 | 204Pb(40Ar,3n) |
| 242Fm | 1975 | 204Pb(40Ar,2n), 206Pb(40Ar,4n) |
| 243Fm | 1981 | 206Pb(40Ar,3n) |
| 244Fm | 1967 | 233U(16O,5n) |
| 245Fm | 1967 | 233U(16O,4n) |
| 246Fm | 1966 | 235U(16O,5n) |
| 247Fm | 1967 | 239Pu(12C,4n) |
| 248Fm | 1958 | 240Pu(12C,4n) |
| 249Fm | 1960 | 238U(16O,5n) |
| 250Fm | 1954 | 238U(16O,4n) |
| 251Fm | 1957 | 249Cf(α,2n) |
| 252Fm | 1956 | 249Cf(α,n) |
| 253Fm | 1957 | 252Cf(α,3n) |
| 254Fm | 1954 | Neutron capture |
| 255Fm | 1954 | Neutron capture |
| 256Fm | 1955 | Neutron capture |
| 257Fm | 1964 | Neutron capture |
| 258Fm | 1971 | 257Fm(d,p) |
| 259Fm | 1980 | 257Fm(t,p) |
| 260Fm? | 1992? | 254Es+18O, 22Ne — transfer (EC of 260Md) |
260Fm was not confirmed in 1997.
References
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- Isotope masses from:
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- Template:NUBASE 2003
- Half-life, spin, and isomer data selected from the following sources.
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- Template:NUBASE 2003
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- Template:CRC85
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