Isotopes of plutonium

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.^{[note 1]} Like all artificial elements, it has no stable isotopes. It was synthesized before being found in nature, with the first isotope synthesized being ²³⁸Pu in 1940. Twenty-two plutonium radioisotopes have been characterized. The most stable are ²⁴⁴Pu with a half-life of 80.8 million years; ²⁴²Pu with a half-life of 373,300 years; and ²³⁹Pu with a half-life of 24,110 years; and ²⁴⁰Pu with a half-life of 6,560 years. This element also has eight meta states; all have half-lives of less than one second.

The known isotopes of plutonium range from ²²⁶Pu to ²⁴⁷Pu. The primary decay modes before the most stable isotope, ²⁴⁴Pu, are spontaneous fission and alpha decay; the primary mode after is beta emission. The primary decay products before ²⁴⁴Pu are isotopes of uranium and neptunium (not considering fission products), and the primary decay products after are isotopes of americium.

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