Also known as: Rn, niton, radium emanation
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Last Updated: May 22, 2024 • Article History
radon
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Key People:
Sir William Ramsay
Related Topics:
chemical element
noble gas
radon-222
radon-219
radon-220
Radon (Rn), a heavy radioactive of Group 18, generated by the radioactive decay. (Radon was originally called radium emanation.) Radon is a colorless gas, 7.5 times heavier than and more than 100 times heavier than . The gas liquefies at −61.8 °C (−79.2 °F) and freezes at −71 °C (−96 °F). On further cooling, solid radon glows with a soft yellow light that becomes orange-red at the of liquid air (−195 °C [−319 °F]).
Radon is rare in nature because its iare all short-lived and because its source, radium, is a scarce element. The contains traces of radon near the ground as a result of seepage from and , both of which contain minute quantities of radium. (Radium occurs as a natural decay product of present in various types of rocks.)
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By the late 1980s, naturally occurring radon gas had come to be recognized as a potentially serious health hazard. Radioactive decay of uranium in minerals, especially granite, generates radon gas that can diffuse through soil and rock and enter buildings through basements (radon has a higher density than air) and through water supplies derived from wells (radon has a significant solubility in water). The gas can accumulate in the air of poorly ventilated houses. The decay of radon produces radioactive “daughters” (polonium, bismuth, and lead isotopes) that can be ingested from well water or can be absorbed in dust particles and then breathed into the lungs. Exposure to high concentrations of this radon and its daughters over the course of many years can greatly increase the risk of developing lung cancer. Indeed, radon is now thought to be the greatest cause of lung cancer among nonsmokers in the United States. Radon levels are highest in homes built over geological formations that contain uranium mineral deposits.
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