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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