Polonium

Overview

Polonium is a chemical element with the symbol Po and atomic number 84. A rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth. Polonium has been studied for possible use in heating spacecraft. It is a radioactive element and is dangerous to handle in large amounts.

History

Polonium was discovered in July 1898 by Marie and Pierre Curie, when it was extracted from uranium ore and identified solely by its strong radioactivity. Polonium was named after Marie Curie's homeland of Poland.

Characteristics

Polonium is a very rare element in nature because of the short half-life of all its isotopes. It is found in uranium ores at about 0.1 mg per metric ton (1 part in 10^10), which is approximately 0.2% of the abundance of radon. The amounts in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers.

Isotopes

There are 33 known isotopes of polonium with atomic masses that range from 188 to 220 u. All of them are radioactive. Polonium has no stable isotopes, and the radioactive isotopes range in half-life from 0.3 ms (polonium-214) to 103 years (polonium-209).

Applications

Because of its position in the periodic table, polonium can form many chemical compounds where it has oxidation states of +4 and +2. Polonium-210 is the most widely used isotope of polonium. It is a powerful alpha emitter and is used in anti-static devices and for the removal of dust from photographic films. Some of its compounds have been used in laboratory experiments to investigate their possible use in portable nuclear batteries.

Health effects

Polonium is a dangerous and lethal element if ingested or inhaled, and it has been used as a poison in several high-profile deaths. Minute amounts of polonium-210 can be a severe radiation hazard.