Radon-222

Source: Wikipedia, the free encyclopedia.
Radon-222, 222Rn
General
Decay mode
Decay energy (MeV)
Alpha decay5.5904[2]
Isotopes of radon
Complete table of nuclides

Radon-222 (222Rn, Rn-222, historically radium emanation or radon) is the most stable

primordial uranium-238 and is the immediate decay product of radium-226. Radon-222 was first observed in 1899, and was identified as an isotope of a new element several years later. In 1957, the name radon, formerly the name of only radon-222, became the name of the element. Owing to its gaseous nature and high radioactivity, radon-222 is one of the leading causes of lung cancer.[3]

History

Following the 1898 discovery of

uranium series, radon-222, which he called radium emanation.[6]

In the early 20th century, the element radon was known by several different names. Chemist William Ramsay, who extensively studied the element's chemical properties, suggested the name niton, and Rutherford originally suggested emanation. At that time, radon only referred to the isotope 222Rn, whereas the names actinon and thoron denoted 219Rn and 220Rn, respectively.[7] In 1957, the International Union of Pure and Applied Chemistry (IUPAC) promoted the name radon to refer to the element rather than just 222Rn; this was done under a new rule concerning isotope naming conventions.[7] This decision was controversial because it was believed to give undue credit to Dorn's identification of radon-222 over Rutherford's identification of radon-220, and the historical use of the name radon created confusion as to whether the element or the isotope 222Rn was being discussed.[7]

Decay properties

The decay chain of uranium-238, known as the uranium series or radium series, of which radon-222 is a member.

Radon-222 is generated in the uranium series from the

lead-206
.

In theory, 222Rn is capable of

partial half-life limits of 8 years for both transitions. If the beta decay of 222Rn is possible, it is predicted to have a very low decay energy (24 ± 21 keV) and thus a half-life on the order of 105 years, also resulting in a very low branching probability relative to alpha decay.[8]

Occurrence and hazards

Main article: Health effects of radon

All radon isotopes are hazardous owing to their radioactivity, gaseous nature, chemical inertness, and radioactivity of their decay products (progeny). Radon-222 is especially dangerous because its longer half-life allows it to permeate soil and rocks, where it is produced in trace quantities from decays of uranium-238, and concentrate in buildings and

cigarette smoking,[3] with over 20,000 deaths per year attributed to radon-induced lung cancer.[9][11]

See also

Notes

  1. ^ AME2016 gives 222Rn a lower mass than 222Fr,[1] which would forbid single beta decay, though it is possible within the given error margin and is explicitly predicted by Belli et al.

References

  1. ^
    doi:10.1088/1674-1137/41/3/030001
    .
  2. ^
    doi:10.1088/1674-1137/41/3/030003
    .
  3. ^ a b c EPA Facts about Radon (PDF) (Report). United States Environmental Protection Agency. pp. 1–3. Retrieved 22 February 2019.
  4. S2CID 12590893
    .
  5. LCCN 2016935977
    .
  6. doi:10.1063/1.2991210. Archived from the original
    (PDF) on 2016-08-24. Retrieved 2019-02-22.
  7. ^
    PMID 23965684
    .
  8. ^
    S2CID 118513731
    .
  9. ^ a b c EPA assessment of risks from radon in homes (PDF) (Report). Office of Radiation and Indoor Air, United States Environmental Protection Agency. 2003.
  10. ^ "Radiation protection: Radium". United States Environmental Protection Agency. Archived from the original on 11 February 2015. Retrieved 22 February 2019.
  11. ^ "Radon Fact Sheet: What it is, how it affects us, why it matters". Air Chek, Inc. Retrieved 22 February 2019.
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