Isotopes of curium explained

Curium (₉₆Cm) 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 ²⁴²Cm in 1944, which has 146 neutrons.

There are 19 known radioisotopes ranging from ²³³Cm to ²⁵¹Cm. There are also ten known nuclear isomers. The longest-lived isotope is ²⁴⁷Cm, 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.^{[1] [2]} The longest-lived isomer is ^246mCm with a half-life of 1.12 seconds.

List of isotopes

|-| rowspan=2|²³³Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 137| rowspan=2|233.05077(8)| rowspan=2|| β⁺ (80%)| ²³³Am| rowspan=2|3/2+#|-| α (20%)| ²²⁹Pu|-| rowspan=3|²³⁴Cm| rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 138| rowspan=3|234.05016(2)| rowspan=3|52(9) s| β⁺ (71%)| ²³⁴Am| rowspan=3|0+|-| α (27%)| ²³⁰Pu|-| SF (2%)| (various)|-| rowspan=2|²³⁵Cm^[3] | rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 139| rowspan=2|235.05143(22)#| rowspan=2|| β⁺ (99.0%)| ²³⁵Am| rowspan=2|(5/2+)|-| α (1.0%)| ²³¹Pu|-| rowspan=3|²³⁶Cm| rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 140| rowspan=3|236.05141(22)#| rowspan=3|6.8(8) min| β⁺ (82%)| ²³⁶Am| rowspan=3|0+|-| α (18%)| ²³²Pu|-| SF (<0.1%)^[4] | (various)|-| rowspan=2|²³⁷Cm^{[5] [3]} | rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 141| rowspan=2|237.05290(22)#| rowspan=2|>660 s| β⁺| ²³⁷Am| rowspan=2|(5/2+)|-| α (<1%)| ²³³Pu|-| rowspan=2|²³⁸Cm^[5] | rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 142| rowspan=2|238.05303(4)| rowspan=2|2.2(4) h| EC (~94%)| ²³⁸Am| rowspan=2|0+|-| α (~6%)| ²³⁴Pu|-| rowspan=2|²³⁹Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 143| rowspan=2|239.05496(11)#| rowspan=2|2.5(4) h| β⁺| ²³⁹Am| rowspan=2|(7/2−)|-| α (6.2x10⁻³%)| ²³⁵Pu|-| rowspan=3|²⁴⁰Cm| rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 144| rowspan=3|240.0555295(25)| rowspan=3|27(1) d| α (99.5%)| ²³⁶Pu| rowspan=3|0+|-| EC (.5%)| ²⁴⁰Am|-| SF (3.9×10⁻⁶%)| (various)|-| rowspan=2|²⁴¹Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 145| rowspan=2|241.0576530(23)| rowspan=2|32.8(2) d| EC (99%)| ²⁴¹Am| rowspan=2|1/2+|-| α (1%)| ²³⁷Pu|-| rowspan=3|²⁴²Cm^[6] | rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 146| rowspan=3|242.0588358(20)| rowspan=3|162.8(2) d| α| ²³⁸Pu| rowspan=3|0+|-| SF (6.33×10⁻⁶%)| (various)|-| CD (10⁻¹⁴%)^[7] | ²⁰⁸Pb
³⁴Si|-| style="text-indent:1em" | ^242mCm| colspan="3" style="text-indent:2em" | 2800(100) keV| 180(70) ns| | | |-| rowspan=3|²⁴³Cm| rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 147| rowspan=3|243.0613891(22)| rowspan=3|29.1(1) y| α (99.71%)| ²³⁹Pu| rowspan=3|5/2+|-| EC (.29%)| ²⁴³Am|-| SF (5.3×10⁻⁹%)| (various)|-| style="text-indent:1em" | ^243mCm| colspan="3" style="text-indent:2em" | 87.4(1) keV| 1.08(3) μs| IT| ²⁴³Cm| 1/2+|-| rowspan=2|²⁴⁴Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 148| rowspan=2|244.0627526(20)| rowspan=2|18.10(2) y| α| ²⁴⁰Pu| rowspan=2|0+|-| SF (1.34×10⁻⁴%)| (various)|-| style="text-indent:1em" | ^244m1Cm| colspan="3" style="text-indent:2em" | 1040.188(12) keV| 34(2) ms| IT| ²⁴⁴Cm| 6+|-| style="text-indent:1em" | ^244m2Cm| colspan="3" style="text-indent:2em" | 1100(900)# keV| >500 ns| SF| (various)| |-| rowspan=2|²⁴⁵Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 149| rowspan=2|245.0654912(22)| rowspan=2|8.5(1)×10³ y| α| ²⁴¹Pu| rowspan=2|7/2+|-| SF (6.1×10⁻⁷%)| (various)|-| style="text-indent:1em" | ^245mCm| colspan="3" style="text-indent:2em" | 355.92(10) keV| 290(20) ns| IT| ²⁴⁵Cm| 1/2+|-| rowspan=2|²⁴⁶Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 150| rowspan=2|246.0672237(22)| rowspan=2|4.76(4)×10³ y| α (99.97%)| ²⁴²Pu| rowspan=2|0+|-| SF (.0261%)| (various)|-| style="text-indent:1em" | ^246mCm| colspan="3" style="text-indent:2em" | 1179.66(13) keV| 1.12(0.24) s| IT| ²⁴⁶Cm| 8−|-| ²⁴⁷Cm| style="text-align:right" | 96| style="text-align:right" | 151| 247.070354(5)| 1.56(5)×10⁷ y| α| ²⁴³Pu| 9/2−|-| style="text-indent:1em" | ^247m1Cm| colspan="3" style="text-indent:2em" | 227.38(19) keV| 26.3(0.3) μs| IT| ²⁴⁷Cm| 5/2+|-| style="text-indent:1em" | ^247m2Cm| colspan="3" style="text-indent:2em" | 404.90(3) keV| 100.6(0.6) ns| IT| ²⁴⁷Cm| 1/2+|-| rowspan=2|²⁴⁸Cm| rowspan=2 style="text-align:right" | 96| rowspan=2 style="text-align:right" | 152| rowspan=2|248.072349(5)| rowspan=2|3.48(6)×10⁵ y| α (91.74%)| ²⁴⁴Pu| rowspan=2|0+|-| SF (8.26%)| (various)|-| style="text-indent:1em" | ^248mCm| colspan="3" style="text-indent:2em" | 1458.1(1) keV| 146(18) μs| IT| ²⁴⁸Cm| (8−)|-| ²⁴⁹Cm| style="text-align:right" | 96| style="text-align:right" | 153| 249.075953(5)| 64.15(3) min| β⁻| ²⁴⁹Bk| 1/2(+)|-| style="text-indent:1em" | ^249mCm| colspan="3" style="text-indent:2em" | 48.758(17) keV| 23 μs| α| ²⁴⁵Pu| (7/2+)|-| rowspan=3|²⁵⁰Cm| rowspan=3 style="text-align:right" | 96| rowspan=3 style="text-align:right" | 154| rowspan=3|250.078357(12)| rowspan=3|8300# y| SF (74%)^[8] | (various)| rowspan=3|0+|-| α (18%)| ²⁴⁶Pu|-| β⁻ (8%)| ²⁵⁰Bk|-| ²⁵¹Cm| style="text-align:right" | 96| style="text-align:right" | 155| 251.082285(24)| 16.8(2) min| β⁻| ²⁵¹Bk| (1/2+)

Actinides vs fission products

References

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6. Most common isotopes
7. Heaviest known nuclide to undergo cluster decay
8. The nuclide with the lowest atomic number known to undergo spontaneous fission as the main decay mode

• Isotope masses from:
  • • Half-life, spin, and isomer data selected from the following sources.