Polonium (element Po)

Physical and chemical characteristics

Polonium behaves chemically as a metalloid and in metallic form appears silvery but tarnishes readily in air. Its radioactivity produces heat and can cause the metal to self-warm at macroscopic quantities; it also has appreciable vapor pressure for a metal, which increases handling hazard. Chemically, polonium can form compounds in a few oxidation states and shares some similarities with tellurium and bismuth in behavior. General property tables are available at chemical property resources.

Isotopes and natural occurrence

There are dozens of known polonium isotopes; all are radioactive and range widely in half-life. The most commonly referenced isotope in literature and incidents is polonium-210, which is produced in nature by decay chains and is also made artificially. Because of short half-lives, naturally occurring concentrations are extremely low, and most usable polonium is isolated from uranium ores or manufactured in nuclear reactors. For isotope data, consult isotope references and decay charts at decay data.

Production and applications

Polonium is typically prepared by irradiating bismuth targets with neutrons in a reactor or by extracting minute amounts from uranium ores where it appears as a transient decay product. Its strong alpha emission has led to niche uses where a compact alpha source is required. Historically, small amounts were used in anti-static brushes and for eliminating static charge in industrial settings. Polonium has also been used in specialized neutron initiators when combined with beryllium in legacy nuclear technology; descriptions of historical uses and manufacturing context can be found at technology histories and radiation use.

Health, safety and regulation

All polonium isotopes are highly radiotoxic if ingested or inhaled because alpha radiation deposits large amounts of energy over a short distance in tissue. Even microgram quantities can pose severe health risks. Because of its toxicity and potential for misuse, production, transport and possession are tightly regulated in most countries and require specialized facilities and training. For occupational safety guidance and regulatory information, see safety guidance and regulatory summaries.

History and notable facts

Marie and Pierre Curie named the element after Poland, Marie Curie’s homeland. Polonium has appeared in the public record both as an object of scientific study and in a few high-profile poisoning cases that highlighted its lethality and the difficulties of detection and cleanup. For accounts of historical incidents and analysis, consult historical records and case studies.

• Key points: rare, radioactive, all isotopes unstable.
• Common isotope referenced: polonium-210.
• Primary concerns: radiological toxicity and regulatory control.