Polonium << puh LOH nee uhm >> is a rare, radioactive chemical element. Many chemists classify it as a metalloid, but some consider it to be a metal. For information on the position of polonium on the periodic table, see the article Periodic table.
Polonium occurs naturally in the uranium ore pitchblende. But most polonium is made artificially by bombarding bismuth, a brittle metal, with neutrons. Scientists use polonium chiefly for nuclear research.
Polonium has the chemical symbol Po. Its atomic number (number of protons) is 84. It melts at 254 °C and boils at 962 °C. Polonium has 29 known isotopes, forms with the same number of protons but different numbers of neutrons. Its most stable isotope has an atomic mass number (total number of protons and neutrons) of 209. That isotope has a half-life of 102 years—that is, due to radioactive decay, only half the atoms in a sample of isotope 209 would still be atoms of that isotope after 102 years.
The French physicists Marie and Pierre Curie discovered the element in 1898. They named the element in honor of Poland, the country of Marie Curie’s birth.
