Overview

Polonium (pronounced /pɵˈloʊniəm/, po-LOH-nee-əm) is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. A rare and highly radioactive metalloid,[1] polonium is chemically similar to bismuth[2] and tellurium, and it occurs in uranium ores. Polonium has been studied for possible use in heating spacecraft. It is unstable; all isotopes of polonium are radioactive. Polonium is very volatile; it will almost completely vaporize at room temperatures.

Polonium 210 (also called Radium F) is an alpha emitter - most recently used to kill Alexander Valterovich Litvinenko, he died [November 23], 2006.

References

Polonium - wikipedia
Los Alamos National Labs