Polonium

Polonium, symbol Po, rare, radioactive metallic element. Polonium is in group 16 (or VIa) of the periodic table. Its atomic number is 84.

The first element to be discovered by means of its radioactivity, polonium was found in pitchblende in 1898 by the French chemist Marie Curie, who named it for her native country, Poland. Polonium is one of the elements in the uranium-radium series of radioactive decay, the first member of which is uranium-238. Polonium occurs in radium-containing ores and is found in isotopic forms with mass numbers ranging from 192 to 218. Polonium 210 (also called radium-F), the only naturally occurring isotope, has a half-life of 138 days. Polonium melts at about 254° C (about 489° F), boils at about 962° C (about 1764° F), and has a relative density of 9.4.

Because most polonium isotopes disintegrate by emitting alpha particles, the element is a good source of pure alpha radiation. It is also used in nuclear research with elements such as beryllium that emit neutrons when bombarded by alpha particles. In printing and photography equipment, polonium is used in devices that ionize the air to eliminate accumulation of electrostatic charges.