what is plutonium

Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. Plutonium has five "common" isotopes, Pu-238, Pu-239, Pu-240, Pu-241, and Pu-242, all of which are "fissionable". Plutonium-239 is one of the three primary fissile isotopes, along with uranium-233 and uranium-235. Plutonium-238 has been used to power batteries for some heart pacemakers, as well as provide a long-lived heat source to power NASA space missions. Plutonium is also a key material in the development of nuclear power. Plutonium is considered toxic, in part, because if it were to be inhaled it could deposit in the lungs and eventually cause damage.