[ rey-don ]

  1. a chemically inert, radioactive gaseous element produced by the decay of radium: emissions produced by outgassing of rock, brick, etc. are a health hazard. Symbol: Rn; atomic number: 86; atomic weight: 222.

Origin of radon

First recorded in 1915–20; rad(ium) + -on2

Words Nearby radon

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How to use radon in a sentence

British Dictionary definitions for radon


/ (ˈreɪdɒn) /

  1. a colourless radioactive element of the rare gas group, the most stable isotope of which, radon-222, is a decay product of radium. It is used as an alpha particle source in radiotherapy. Symbol: Rn; atomic no: 86; half-life of 222 Rn: 3.82 days; valency: 0; density: 9.73 kg/m³; melting pt: –71°C; boiling pt: –61.7°C

Origin of radon

C20: from radium + -on

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for radon


[ dŏn ]

  1. A colorless, odorless, radioactive element in the noble gas group. It is produced by the radioactive decay of radium and occurs in minute amounts in soil, rocks, and the air near the ground. Radon is used as a source of radiation for the treatment of cancer and other diseases. Its most stable isotope is Rn 222 with a half-life of 3.82 days. Atomic number 86; melting point -71°C; boiling point -61.8°C; specific gravity (solid) 4. See Periodic Table.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for radon


[ (ray-don) ]

A colorless, odorless, radioactive gas that is produced by the decay of radium in the soil.

Notes for radon

Radon seeping through the ground and into buildings is a major source of indoor air pollution and may represent a significant risk for lung cancer.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.