Plutonium-246

Main isotopes of plutonium

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct 238Pu trace 87.74 y SF – α 234U 239Pu trace 2.41×104 y SF – α 235U 240Pu trace 6500 y SF – α 236U 241Pu syn 14 y β− 241Am SF – 242Pu syn 3.73×105 y SF – α 238U 244Pu trace 8.08×107 y α 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.

...
Wikipedia