- Polonium (Po) is a rare and highly radioactive metalloid with atomic number 84, belonging to Group 16 of the periodic table, alongside oxygen, sulfur, selenium, and tellurium.
- Its electron configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴, giving it six valence electrons. Polonium exhibits oxidation states of +2, +4, and +6, with +2 being the most stable. A polonium atom contains eighty-four protons, eighty-four electrons, and a variable number of neutrons depending on the isotope.
- The most common isotope is polonium-210 (²¹⁰Po), which contains 126 neutrons and has a half-life of about 138 days.
- Polonium was discovered in 1898 by Marie Curie and Pierre Curie during their research on uranium ores. While analyzing pitchblende (now known as uraninite), they detected a new radioactive element, which Marie Curie named polonium in honor of her homeland, Poland. This discovery was a milestone in radioactivity research and contributed to Marie Curie’s Nobel Prize in Physics in 1903.
- Physically, polonium is a silvery-gray metal that tarnishes quickly when exposed to air. It is volatile and sublimates at high temperatures. It has a melting point of 254 °C (489 °F) and a boiling point of 962 °C (1,764 °F). Polonium is extremely rare in nature, occurring only in trace amounts in uranium ores. Its scarcity means it is typically produced artificially by bombarding bismuth-209 (²⁰⁹Bi) with neutrons in a nuclear reactor.
- Chemically, polonium behaves somewhat like tellurium and selenium, though it is far more metallic in character. It forms compounds such as polonium dioxide (PoO₂) and polonium hydride (PoH₂). Due to its intense radioactivity, the chemistry of polonium is difficult to study, and its compounds are rarely handled outside of specialized laboratories.
- Polonium has very few practical applications because of its extreme toxicity and short half-life. The most notable use is in anti-static devices, where small amounts of polonium-210 are used to eliminate static electricity in industrial equipment. It has also been used as a lightweight heat source in space satellites and thermoelectric power generators, owing to the immense heat released during radioactive decay. However, such uses are limited because of safety concerns and the development of safer alternatives.
- Biologically, polonium is one of the most toxic substances known. Even microscopic amounts of polonium-210 can be lethal if ingested or inhaled, as it emits high-energy alpha particles that cause severe internal damage. Its most infamous case of poisoning occurred in 2006, when former Russian intelligence agent Alexander Litvinenko was assassinated using polonium-210, bringing global attention to its deadly nature.
- Environmentally, polonium is not considered a widespread contaminant due to its rarity and short half-life. It is sometimes found in trace amounts in tobacco smoke, as uranium in soil naturally decays into polonium through the radioactive decay chain. Because of its extreme radioactivity, environmental exposure is rare and generally only poses a risk in very specific contexts.
