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Curium-248

Main isotopes of curium
Iso­tope Decay
abun­dance half-life mode energy (MeV) pro­duct
242Cm syn 160 d SF
α 6.1 238Pu
243Cm syn 29.1 y α 6.169 239Pu
ε 0.009 243Am
SF
244Cm syn 18.1 y SF
α 5.8048 240Pu
245Cm syn 8500 y SF
α 5.623 241Pu
246Cm syn 4730 y α 5.475 242Pu
SF
247Cm syn 1.56×107 y α 5.353 243Pu
248Cm syn 3.40×105 y α 5.162 244Pu
SF
250Cm syn 9000 y SF
α 5.169 246Pu
β 0.037 250Bk

Curium (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 242Cm in 1944, which has 146 neutrons. All of the isotopes are radioactive.

There are 21 known radioisotopes with atomic masses ranging from 232Cm to 252Cm. There are also four known nuclear isomers (243mCm, 244mCm, 245mCm, and 249mCm). The longest-lived isotope is 247Cm, with a half-life of 15.6 million years – several orders of magnitude longer than the half-life of all known nuclei of elements beyond curium in the periodic table. The shortest-lived isomer is 244mCm with a half-life of 34 milliseconds.

No fission products
have a half-life
in the range of
100–210 k years ...

... nor beyond 15.7 M years

Legend for superscript symbols
₡  has thermal neutron capture cross section in the range of 8–50 barns
ƒ  fissile
metastable isomer
№  naturally occurring radioactive material (NORM)
þ  neutron poison (thermal neutron capture cross section greater than 3k barns)
†  range 4–97 y: Medium-lived fission product
‡  over 200,000 y: Long-lived fission product



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