Polonium
MELTING POINT:
254°C
BOILING POINT:
962°C
DENSITY:
9.32 g/cm
3
MOST COMMON IONS:
Po
2−
, Po
2+
, PoO
3
2−
Polonium is a silver-grey, radioactive metal . Discovered by chemist Marie Curie in 1898, polonium was named after her country of origin (Poland). Curie discovered the element while analyzing samples of pitchblende, or uranium ore, from Bohemia. She found that unrefined pitchblende was more radioactive than the uranium extracted from it. Small amounts of polonium and another radioactive element, radium, were later obtained from the refined ore.
Polonium is found in the earth's crust at exceedingly low levels; its natural abundance is only 2 × 10 −10 milligrams per kilogram. Polonium is produced in pitchblende when the bismuth isotope 210 Bi, which has a half-life of five days, decays into 210 Po. Approximately 100 micrograms of polonium are found in 1 ton of uranium ore. Polonium can also be produced by bombarding 209 Bi with neutrons to form 210 Bi, which in turn decays into 210 Po.
Polonium has more isotopes than any other element. The most common isotope is 210 Po, which has a half-life of 138.4 days. Other isotopes have half-lives ranging from less than 1 second to 102 years ( 209 Po). Polonium burns in air to form polonium (IV) oxide (PoO 2 ) and reacts with halogens to form tetrahalides (e.g., PoCl 4 , PoBr 4 , PoI 4 ). It also dissolves readily in dilute acids.
Polonium is a strong emitter of α -particles ; approximately 1 gram of 210 Po emits 140 watts of heat energy. For this reason, it is used as a source of thermoelectric power in satellites. It is also utilized as a source of neutrons (when mixed with beryllium), as an antistatic device in industrial equipment, and in brushes that remove dust from photographic film.
SEE ALSO Curie, Marie Sklodowska ; Halogens ; Radioactivity ; Radium ; Uranium .
Stephanie Dionne Sherk
Bibliography
Lide, David R., ed. (2003). In The CRC Handbook of Chemistry and Physics , 84th edition. Boca Raton, FL: CRC Press.
Internet Resources
Gagnon, Steve. "Polonium." Thomas Jefferson National Accelerator Facility (Jefferson Lab). Available from http://education.jlab.org/itselemental/ele084.html .