What Is Polonium?
QUICK ANSWER
Polonium is a chemical element with atomic number 84 and the symbol Po. It's a rare, highly radioactive metalloid that exists in trace amounts in uranium ores. Polonium is one of the most dangerous substances known by weight, infamous for its use in the 2006 assassination of Russian dissident Alexander Litvinenko.
Polonium has one of the more dramatic histories of any element. Marie and Pierre Curie discovered it in 1898 while sifting through tons of pitchblende, naming it after Marie's homeland of Poland. A century later, polonium became infamous as the poison that killed a former Russian intelligence officer in London. The element is so dangerously radioactive that microscopic amounts can be lethal.
Where is polonium on the periodic table?
Polonium has atomic number 84, the symbol Po, and sits in group 16 of the periodic table alongside oxygen, sulfur, selenium, and tellurium. It's classified as a metalloid with some metallic properties. All polonium isotopes are radioactive, with Po-210 being the most common, having a half-life of 138 days. Polonium was discovered in 1898 by Marie and Pierre Curie during their work isolating radium from uranium ore. The Curies named it after Poland, Marie's birthplace, in a political statement to draw attention to Poland's lack of independence at the time.
What are the properties of polonium?
Polonium is silvery-gray and melts at 254°C, with a density of 9.20 g/cm³. The element exists in two solid phases at room temperature. Most properties are difficult to measure because polonium samples constantly destroy themselves through radioactive decay heat, which can melt or vaporize small amounts. A single gram of polonium-210 generates about 140 watts of heat continuously from radioactive decay, glowing visibly blue from the ionization of surrounding air. Polonium is chemically similar to tellurium and bismuth but is rarely studied because of the extreme handling difficulties.
Why is polonium so dangerous?
Polonium-210 emits alpha radiation, which doesn't penetrate skin but is devastating if inhaled or ingested. Once inside the body, alpha particles damage cells locally with extreme intensity. Polonium is estimated to be about 250 billion times more toxic by mass than hydrogen cyanide. A lethal dose for an adult is on the order of micrograms. The element accumulates in soft tissues and decays slowly, causing massive radiation damage over weeks. There is no effective treatment once a significant amount has been absorbed, which is why polonium poisoning is almost always fatal.
What is polonium used for?
Polonium has very limited legitimate uses because of its extreme danger and short half-life. Anti-static brushes for photography and lab work used polonium-210 to ionize air and dissipate static electricity, though most of these have been replaced with safer alternatives. Some historical neutron sources combined polonium with beryllium to generate neutrons for research. Spacecraft once considered polonium as a thermal power source. The element has no medical applications and is not used in nuclear weapons or commercial power generation. Most produced polonium ends up in highly restricted research.
Polonium is the radioactive element that started as a Curie discovery and ended up as a state-level assassination tool. Its combination of extreme radioactivity, manageable chemistry, and untraceable use makes it one of the most feared materials in modern science. Few elements span such a range from triumphant discovery to chilling weapon.
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