Polonium is a rare, highly radioactive chalcogen named after Poland. Discovered by Marie and Pierre Curie in 1898, metallic polonium is a silvery post-transition metal and a strong alpha emitter used historically in antistatic devices and specialized heat sources. Extreme radiotoxicity makes it hazardous, especially if ingested or inhaled.
Polonium was discovered in 1898 by Marie and Pierre Curie while studying uranium ores (pitchblende). They named it after Marie Curie’s homeland, Poland (Polonia), to honor her native country’s struggle for independence.
Polonium has no stable isotopes; all of its isotopes are radioactive. The most common isotope, Polonium-210 (\(^{210}\mathrm{Po}\)), decays by emitting alpha particles:
\(\mathrm{^{210}Po \rightarrow ^{206}Pb + \alpha}\)
This decay releases significant energy but has a short half-life of about 138 days.
Although rare and dangerous, polonium has been used in:
Due to its toxicity and radioactivity, its use is now highly restricted.
Polonium is one of the most radiotoxic substances known. When ingested or inhaled, it emits alpha radiation that damages internal organs and tissues. Even microgram quantities can be fatal, as alpha particles cause severe biological damage within the body.
Polonium exhibits oxidation states of −2, +2, +4, and +6, similar to other chalcogens. The +4 oxidation state is most stable. For example, in polonium dioxide (PoO2), it exhibits a +4 oxidation state:
\(\mathrm{Po + O_2 \rightarrow PoO_2}\)
Polonium is a silvery-gray, brittle metal with a melting point of 254 °C and a boiling point of 962 °C. It is volatile and can form polonium vapor, which is also highly radioactive and dangerous to inhale.
Polonium is extremely rare in nature and is primarily produced artificially by bombarding bismuth-209 with neutrons in a nuclear reactor:
\(\mathrm{^{209}Bi + n \rightarrow ^{210}Bi \xrightarrow{\beta^-} ^{210}Po}\)
This process yields polonium-210, which is then separated chemically.
Handling polonium is dangerous due to its alpha radiation and vapor toxicity. It must be handled in sealed environments with remote tools, protective suits, and proper ventilation. Ingestion or inhalation can lead to acute radiation syndrome and death.
Polonium belongs to the chalcogen group because it has six valence electrons (ns2np4 configuration), similar to oxygen, sulfur, selenium, and tellurium. However, due to its metallic character, it behaves more like a post-transition metal.
Yes, polonium has been used in the past as a neutron initiator in early nuclear weapons. Its ability to emit alpha particles that react with beryllium to release neutrons makes it suitable for such applications. However, it is now replaced by safer materials.
Polonium reacts with hydrogen to form polonium hydride (H2Po), a volatile and unstable compound:
\(\mathrm{Po + H_2 \rightarrow H_2Po}\)
It decomposes easily and is rarely encountered outside laboratory research due to its instability and radioactivity.