# Isotopes of curium

Curium ($_{96}$Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was $^{242}$Cm in 1944, which has 146 neutrons.
There are 19 known radioisotopes ranging from $^{233}$Cm to $^{251}$Cm. There are also ten known nuclear isomers. The longest-lived isotope is $^{247}$Cm, with half-life 15.6 million years – orders of magnitude longer than that of any known isotope beyond curium, and long enough to study as a possible extinct radionuclide that would be produced by the r-process. The longest-lived known isomer is $^{246m}$Cm with a half-life of 1.12 seconds.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity |
| Spin and parity |||
| $^{233}$Cm | 96 | 137 | 233.050771(87) | 27(10) s | β$^+$ (80%) | $^{233}$Am | 3/2+# |
| $^{233}$Cm | 96 | 137 | 233.050771(87) | 27(10) s | α (20%) | $^{229}$Pu | 3/2+# |
| $^{234}$Cm | 96 | 138 | 234.050159(18) | 52(9) s | β$^+$ (71%) | $^{234}$Am | 0+ |
| $^{234}$Cm | 96 | 138 | 234.050159(18) | 52(9) s | α (27%) | $^{230}$Pu | 0+ |
| $^{234}$Cm | 96 | 138 | 234.050159(18) | 52(9) s | SF (2%) | (various) | 0+ |
| $^{235}$Cm | 96 | 139 | 235.05155(11)# | 7(3) min | β$^+$ (96%) | $^{235}$Am | 5/2+# |
| $^{235}$Cm | 96 | 139 | 235.05155(11)# | 7(3) min | α (4%) | $^{231}$Pu | 5/2+# |
| $^{236}$Cm | 96 | 140 | 236.051372(19) | 6.8(8) min | β$^+$ (82%) | $^{236}$Am | 0+ |
| $^{236}$Cm | 96 | 140 | 236.051372(19) | 6.8(8) min | α (18%) | $^{232}$Pu | 0+ |
| $^{237}$Cm | 96 | 141 | 237.052869(80) | >10# min | α (?%) | $^{233}$Pu | 5/2+# |
| $^{238}$Cm | 96 | 142 | 238.053082(13) | 2.2(4) h | EC (96.11%) | $^{238}$Am | 0+ |
| $^{238}$Cm | 96 | 142 | 238.053082(13) | 2.2(4) h | α (3.84%) | $^{234}$Pu | 0+ |
| $^{238}$Cm | 96 | 142 | 238.053082(13) | 2.2(4) h | SF (0.048%) | (various) | 0+ |
| $^{239}$Cm | 96 | 143 | 239.05491(16) | 2.5(4) h | β$^+$ | $^{239}$Am | 7/2−# |
| $^{239}$Cm | 96 | 143 | 239.05491(16) | 2.5(4) h | α (6.2x10$^{−3}$%) | $^{235}$Pu | 7/2−# |
| $^{240}$Cm | 96 | 144 | 240.0555282(20) | 30.4(37) d | α | $^{236}$Pu | 0+ |
| $^{240}$Cm | 96 | 144 | 240.0555282(20) | 30.4(37) d | SF (3.9×10$^{−6}$%) | (various) | 0+ |
| $^{241}$Cm | 96 | 145 | 241.0576512(17) | 32.8(2) d | EC (99.0%) | $^{241}$Am | 1/2+ |
| $^{241}$Cm | 96 | 145 | 241.0576512(17) | 32.8(2) d | α (1.0%) | $^{237}$Pu | 1/2+ |
| $^{242}$Cm | 96 | 146 | 242.0588342(12) | 162.8(2) d | α | $^{238}$Pu | 0+ |
| $^{242}$Cm | 96 | 146 | 242.0588342(12) | 162.8(2) d | SF (6.2×10$^{−6}$%) | (various) | 0+ |
| $^{242}$Cm | 96 | 146 | 242.0588342(12) | 162.8(2) d | CD (1.1×10$^{−14}$%) | $^{208}$Pb $^{34}$Si | 0+ |
| $^{242m}$Cm | 2800(100) keV | 2800(100) keV | 2800(100) keV | 180(70) ns | | | |
| $^{243}$Cm | 96 | 147 | 243.0613873(16) | 29.1(1) y | α (99.71%) | $^{239}$Pu | 5/2+ |
| $^{243}$Cm | 96 | 147 | 243.0613873(16) | 29.1(1) y | EC (0.29%) | $^{243}$Am | 5/2+ |
| $^{243}$Cm | 96 | 147 | 243.0613873(16) | 29.1(1) y | SF (5.3×10$^{−9}$%) | (various) | 5/2+ |
| $^{243m}$Cm | 87.4(1) keV | 87.4(1) keV | 87.4(1) keV | 1.08(3) μs | IT | $^{243}$Cm | 1/2+ |
| $^{244}$Cm | 96 | 148 | 244.0627506(12) | 18.11(3) y | α | $^{240}$Pu | 0+ |
| $^{244}$Cm | 96 | 148 | 244.0627506(12) | 18.11(3) y | SF (1.37×10$^{−4}$%) | (various) | 0+ |
| $^{244m1}$Cm | 1040.181(11) keV | 1040.181(11) keV | 1040.181(11) keV | 34(2) ms | IT | $^{244}$Cm | 6+ |
| $^{244m2}$Cm | 1100(900)# keV | 1100(900)# keV | 1100(900)# keV | >500 ns | SF | (various) | |
| $^{245}$Cm | 96 | 149 | 245.0654910(12) | 8250(70) y | α | $^{241}$Pu | 7/2+ |
| $^{245}$Cm | 96 | 149 | 245.0654910(12) | 8250(70) y | SF (6.1×10$^{−7}$%) | (various) | 7/2+ |
| $^{245m}$Cm | 355.92(10) keV | 355.92(10) keV | 355.92(10) keV | 290(20) ns | IT | $^{245}$Cm | 1/2+ |
| $^{246}$Cm | 96 | 150 | 246.0672220(16) | 4706(40) y | α (99.97%) | $^{242}$Pu | 0+ |
| $^{246}$Cm | 96 | 150 | 246.0672220(16) | 4706(40) y | SF (0.02615%) | (various | 0+ |
| $^{246m}$Cm | 1179.66(13) keV | 1179.66(13) keV | 1179.66(13) keV | 1.12(24) s | IT | $^{246}$Cm | 8− |
| $^{247}$Cm | 96 | 151 | 247.0703527(41) | 1.56(5)×10$^7$ y | α | $^{243}$Pu | 9/2− |
| $^{247m1}$Cm | 227.38(19) keV | 227.38(19) keV | 227.38(19) keV | 26.3(3) μs | IT | $^{247}$Cm | 5/2+ |
| $^{247m2}$Cm | 404.90(3) keV | 404.90(3) keV | 404.90(3) keV | 100.6(6) ns | IT | $^{247}$Cm | 1/2+ |
| $^{248}$Cm | 96 | 152 | 248.0723491(25) | 3.48(6)×10$^5$ y | α (91.61%) | $^{244}$Pu | 0+ |
| $^{248}$Cm | 96 | 152 | 248.0723491(25) | 3.48(6)×10$^5$ y | SF (8.39%) | (various) | 0+ |
| $^{248m}$Cm | 1458.1(10) keV | 1458.1(10) keV | 1458.1(10) keV | 146(18) μs | IT | $^{248}$Cm | 8−# |
| $^{249}$Cm | 96 | 153 | 249.0759540(25) | 64.15(3) min | β$^−$ | $^{249}$Bk | 1/2+ |
| $^{249m}$Cm | 48.76(4) keV | 48.76(4) keV | 48.76(4) keV | 23 μs | α | $^{245}$Pu | 7/2+ |
| $^{250}$Cm | 96 | 154 | 250.078358(11) | 8300# y | SF (74%) | (various) | 0+ |
| $^{250}$Cm | 96 | 154 | 250.078358(11) | 8300# y | α (?%) | $^{246}$Pu | 0+ |
| $^{250}$Cm | 96 | 154 | 250.078358(11) | 8300# y | β$^−$ (?%) | $^{250}$Bk | 0+ |
| $^{251}$Cm | 96 | 155 | 251.082285(24) | 16.8(2) min | β$^−$ | $^{251}$Bk | (3/2+) |
| This table header & footer: view ||||||||
* ↑ $^m$Cm – 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).
* 1 2 3 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Modes of decay: CD:Cluster decay EC:Electron capture SF:Spontaneous fission
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* ↑ Theoretically capable of β$^+$β$^+$ decay to $^{242}$Pu
* ↑ Heaviest known nuclide to undergo cluster decay
* ↑ Theoretically capable of β$^−$β$^−$ decay to $^{248}$Cf
* ↑ The nuclide with the lowest atomic number known to undergo spontaneous fission as the main decay mode

## Actinides vs fission products

Actinides and fission products by half-life vte :
| Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Actinides by decay chain | Half-life range (a) | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield | Fission products of $^{235}$U by yield |
| 4n | 4n + 1 | 4n + 2 | 4n + 3 | Half-life range (a) | 4.5–7% | 0.04–1.25% | <0.001% |
| Ra$^№$ | | | | 4–6 a | | Eu$^þ$ | |
| Bk | | | | > 9 a | | | |
| Cm$^ƒ$ | Pu$^ƒ$ | Cf | Ac$^№$ | 10–29 a | Sr | Kr | Cd$^þ$ |
| U$^ƒ$ | | Pu$^ƒ$ | Cm$^ƒ$ | 29–97 a | Cs | Sm$^þ$ | Sn |
| | Cf$^ƒ$ | Am$^ƒ$ | | 141–351 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Am$^ƒ$ | | Cf$^ƒ$ | 430–900 a | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Ra$^№$ | Bk | 1.3–1.6 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Pu | Th | Cm$^ƒ$ | Am$^ƒ$ | 4.7–7.4 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | Cm$^ƒ$ | Cm | | 8.3–8.5 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | | Pu$^ƒ$ | 24.1 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| | | Th$^№$ | Pa$^№$ | 32–76 ka | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... | No fission products have a half-life in the range of 100 a–210 ka ... |
| Np$^ƒ$ | U$^ƒ$ | U$^№$ | | 150–250 ka | Tc$^₡$ | Sn |
| Cm | | Pu | | 327–375 ka | | Se$^₡$ |
| | | | | 1.33 Ma | Cs$^₡$ |
| | Np$^ƒ$ | | | 1.61–6.5 Ma | Zr | Pd |
| U | | | Cm$^ƒ$ | 15–24 Ma | | I$^₡$ |
| Pu | | | | 80 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| Th$^№$ | | U$^№$ | U$^{ƒ№}$ | 0.7–14.1 Ga | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma | ... nor beyond 15.7 Ma |
| ₡, has thermal neutron capture cross section in the range of 8–50 barnsƒ, fissile№, primarily a naturally occurring radioactive material (NORM)þ, neutron poison (thermal neutron capture cross section greater than 3k barns) |||||||||