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Isotopes of californium
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Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 898 years.
List of isotopes
| Nuclide [n 1] |
Z | N | Isotopic mass (Da)[3] [n 2][n 3] |
Half-life[4] |
Decay mode[4] [n 4] |
Daughter isotope |
Spin and parity[4] [n 5][n 6] | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy | |||||||||||||||||||
| 237Cf | 98 | 139 | 237.06220(10) | 0.8(2) s | α (70%) | 233Cm | 5/2+# | ||||||||||||
| SF (30%) | (various) | ||||||||||||||||||
| β+ (rare) | 237Bk | ||||||||||||||||||
| 238Cf | 98 | 140 | 238.06149(32)# | 21.1(13) ms | SF[n 7] | (various) | 0+ | ||||||||||||
| α (<5%) | 234Cm | ||||||||||||||||||
| 239Cf[5] | 98 | 141 | 239.06248(13)# | 28(2) s | α (65%) | 235Cm | (5/2+) | ||||||||||||
| β+ (35%) | 239Bk | ||||||||||||||||||
| 240Cf | 98 | 142 | 240.062253(19) | 40.3(9) s | α (98.5%) | 236Cm | 0+ | ||||||||||||
| SF (1.5%) | (various) | ||||||||||||||||||
| β+? | 240Bk | ||||||||||||||||||
| 241Cf[5] | 98 | 143 | 241.06369(18)# | 2.35(18) min | β+ (85%) | 241Bk | (7/2−) | ||||||||||||
| α (15%) | 237Cm | ||||||||||||||||||
| 242Cf | 98 | 144 | 242.063755(14) | 3.49(15) min | α (61%) | 238Cm | 0+ | ||||||||||||
| β+ (39%) | 242Bk | ||||||||||||||||||
| SF (<0.014%) | (various) | ||||||||||||||||||
| 243Cf | 98 | 145 | 243.06548(19)# | 10.8(3) min | β+ (86%) | 243Bk | (1/2+) | ||||||||||||
| α (14%) | 239Cm | ||||||||||||||||||
| 244Cf | 98 | 146 | 244.0659994(28) | 19.5(5) min | α (75%) | 240Cm | 0+ | ||||||||||||
| EC (25%) | 244Bk | ||||||||||||||||||
| 245Cf | 98 | 147 | 245.0680468(26) | 45.0(15) min | β+ (64.7%) | 245Bk | 1/2+ | ||||||||||||
| α (35.3%) | 241Cm | ||||||||||||||||||
| 245mCf | 57(4) keV | >100# ns | IT | 245Cf | (7/2+) | ||||||||||||||
| 246Cf | 98 | 148 | 246.0688037(16) | 35.7(5) h | α | 242Cm | 0+ | ||||||||||||
| SF (2.4×10−4%) | (various) | ||||||||||||||||||
| EC? | 246Bk | ||||||||||||||||||
| 247Cf | 98 | 149 | 247.070971(15) | 3.11(3) h | EC (99.965%) | 247Bk | (7/2+) | ||||||||||||
| α (.035%) | 243Cm | ||||||||||||||||||
| 248Cf | 98 | 150 | 248.0721829(55) | 333.5(28) d | α (99.997%) | 244Cm | 0+ | ||||||||||||
| SF (.0029%) | (various) | ||||||||||||||||||
| 249Cf | 98 | 151 | 249.0748504(13) | 351(2) y | α | 245Cm | 9/2− | ||||||||||||
| SF (5×10−7%) | (various) | ||||||||||||||||||
| 249mCf | 144.98(5) keV | 45(5) μs | IT | 249Cf | 5/2+ | ||||||||||||||
| 250Cf | 98 | 152 | 250.0764045(17) | 13.08(9) y | α (99.923%) | 246Cm | 0+ | ||||||||||||
| SF (.077%) | (various) | ||||||||||||||||||
| 251Cf[n 8] | 98 | 153 | 251.0795872(42) | 898(44) y | α | 247Cm | 1/2+ | ||||||||||||
| 251mCf | 370.47(3) keV | 1.3(1) μs | IT | 251Cf | 11/2− | ||||||||||||||
| 252Cf[n 9] | 98 | 154 | 252.0816265(25) | 2.645(8) y | α (96.8972%) | 248Cm | 0+ | ||||||||||||
| SF (3.1028%)[n 10] | (various) | ||||||||||||||||||
| 253Cf | 98 | 155 | 253.0851337(46) | 17.81(8) d | β− (99.69%) | 253Es | (7/2+) | ||||||||||||
| α (.31%) | 249Cm | ||||||||||||||||||
| 254Cf | 98 | 156 | 254.087324(12) | 60.5(2) d | SF (99.69%) | (various) | 0+ | ||||||||||||
| α (.31%) | 250Cm | ||||||||||||||||||
| β−β−? | 254Fm | ||||||||||||||||||
| 255Cf | 98 | 157 | 255.09105(22)# | 85(18) min | β− | 255Es | (7/2+) | ||||||||||||
| SF? | (various) | ||||||||||||||||||
| α? | 251Cm | ||||||||||||||||||
| 256Cf | 98 | 158 | 256.09344(34)# | 12.3(12) min | SF | (various) | 0+ | ||||||||||||
| α? | 252Cm | ||||||||||||||||||
| β−β−? | 256Fm | ||||||||||||||||||
| This table header & footer: | |||||||||||||||||||
- ^ mCf – Excited nuclear isomer.
- ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- ^
Modes of decay:
EC: Electron capture SF: Spontaneous fission - ^ ( ) spin value – Indicates spin with weak assignment arguments.
- ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- ^ Lightest nuclide known to undergo spontaneous fission as its main decay mode
- ^ High neutron cross-section, tends to absorb neutrons
- ^ Most common isotope
- ^ High neutron emitter, average 3.7 neutrons per fission