Standard Article

Radon: Radionuclides

  1. Bliss L. Tracy

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0428

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Tracy, B. L. 2011. Radon: Radionuclides. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. Radiation Protection Bureau Health Canada, Ottawa, ON, Canada

Publication History

  1. Published Online: 15 DEC 2011


Radon is a naturally occurring radioactive gas formed by the decay of uranium and thorium in the Earth's crust. At atomic number 86, it is the heaviest member of the noble or inert gas family, which also includes helium, neon, argon, krypton, and xenon. Unlike the other members of the family, radon has no stable isotopes. Of the 34 known radioactive isotopes of radon, only three are supported by the decay of primordial radionuclides, and only two occur with any significant abundance in nature. The three isotopes, along with their half-lives, are 222Rn (3.8235 days), 220Rn (55.6 s), and 219Rn (3.96 s). Both 222Rn and 220Rn decay by the emission of α-particles and give rise to a number of short-lived progeny. 222Rn and 220Rn are the only ones regarded as having any health impacts and this is due to their short-lived progeny—218Po, 214Pb, 214Bi, and 214Po from 222Rn; 216Po, 212Pb, 212Bi, 212Po, and 208Tl from 220Rn. Being a gas, radon diffuses readily into the atmosphere and may build up to hazardous concentrations in confined spaces in homes and underground mines. Radon is the largest single contributor to natural background radiation exposure worldwide. Radon is now recognized as the second leading cause of lung cancer, following tobacco smoking, and is responsible for up to 20 000 deaths per year in the United States and 1900 deaths per year in Canada. Many countries have now established programs to reduce radon exposures to the population.


  • 222Rn, α-decay;
  • aerosols;
  • lung cancer;
  • remediation;
  • 218Po;
  • 214Pb;
  • 214Bi;
  • 214Po;
  • 216Po;
  • 212Pb;
  • 212Bi;
  • 212Po;
  • 208Tl