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Plutonium-228

Main isotopes of plutonium
iso NA half-life DM DE (MeV) DP
238Pu trace 87.74 y SF 204.66
α 5.5 234U
239Pu trace 2.41×104 y SF 207.06
α 5.157 235U
240Pu syn 6500 y SF 205.66
α 5.256 236U
241Pu syn 14 y β 0.02078 241Am
SF 210.83
242Pu syn 3.73×105 y SF 209.47
α 4.984 238U
244Pu syn 8.08×107 y α 4.666 240U
SF

Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940. Twenty plutonium radioisotopes have been characterized. The most stable are Pu-244, with a half-life of 80.8 million years, Pu-242, with a half-life of 373,300 years, and Pu-239, with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. This element also has eight meta states, though none are very stable; all meta states have half-lives of less than one second.

The isotopes of plutonium range in atomic weight from 228.0387 u (Pu-228) to 247.074 u (Pu-247). The primary decay modes before the most stable isotope, Pu-244, are spontaneous fission and alpha emission; the initial mode after is beta emission. The primary decay products before Pu-244 are isotopes of uranium and neptunium (neglecting the wide range of daughter nuclei created by fission processes), and the primary products after are isotopes of americium.


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