Radon
Radon, a radioactive, colorless, odorless, gaseous element. Radon is the heaviest known gas and is inert (will not normally combine with any other element). Of the 20 known isotopes, radon 222 is the most stable, with a half-life of 3.8 days.
Radon is formed by the decay of radium and occurs naturally in soil in varying concentrations. Through sumps and cracks, it can seep into basements and accumulate. The accumulated radon, though radioactive, is not itself dangerous. However, it decays into other radioactive substances, such as polonium, that are a health hazard. Atoms of these substances, unlike atoms of radon, adhere to airborne particles of dust; when inhaled, the dust can remain in the lungs where the radiation emitted by the radioactive substance can cause lung cancer in some persons. In the United States, state and federal environmental agencies provide advice concerning methods for testing and reducing concentrations of radon gas in buildings.
Radon was discovered in 1900 by Friedrich Ernst Dorn, a German scientist, who called the element radium emanation. It was later called niton, and was renamed radon in 1923.
Symbol: Rn. Atomic number: 86. Atomic weight: 222. Specific gravity: gas, 7.55 (air = 1); liquid, 4.4 (water = 1). Melting point: -96 F. (-71.0 C). Boiling point: -79 F. (-61.8 C.). Radon belongs to Group 0 (Inert Gases) of the Periodic Table and has a valence of 0.