Plutonium is a transuranium element, one of the elements that follows uranium in Row 7 of the periodic table. Its atomic number is 94, its atomic mass is 244.0642, and its chemical symbol is Pu.

Properties

All isotopes of plutonium are radioactive. The most stable isotopes are plutonium-242 and plutonium-244 with half lives of 376,300 years and 82,600,000 years respectively. If these isotopes were present when the Earth was created, they would long ago have decayed and disappeared from the Earth's crust. Plutonium is a silvery-white metal with a melting point of 1,183°F (639.5°C) and a density of 19.816 grams per cubic centimeter. The element is very active and forms a number of compounds.

Occurrence and Extraction

Microscopic amounts of plutonium may exist in the Earth's crust as a result of naturally-occurring fusion reactions, but natural sources are of interest only as a matter of curiosity to scientists. For all practical purposes...