Isotopes of radon

There are thirty four known isotopes of Radon (Rn). The most stable isotope is ²²²Rn, which is a decay product (daughter product) of ²²⁶Ra, has a half-life of 3.823 days and emits alpha particles. ²²⁰Rn is a natural decay product of thorium and is called “thoron.” It has a half-life of 55.6 seconds and also emits alpha radiation. ²¹⁹Rn is derived from actinium, is called “actinon,” is an alpha emitter and has a half-life of 3.96 seconds.

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Decay chain

The full decay series of ²³⁸U which produces natural radon is as follows (with half-lives):

²³⁸U (4.5 x 10⁹ yr), ²³⁴Th (24.1 days), ²³⁴Pa (1.18 min), ²³⁴U (2.457 x 10⁵ yr), ²³⁰Th (75,000 yr), ²²⁶Ra (1,600 yr), ²²²Rn (3.82 days), ²¹⁸Po (3.1 min), ²¹⁴Pb (26.8 min), ²¹⁴Bi (19.7 min), ²¹⁴Po (164 µs), ²¹⁰Pb (22.3 yr), ²¹⁰Bi (5.01 days), ²¹⁰Po (138 days), ²⁰⁶Pb (stable).

Older nomenclature

Isotopes of radon occurring within the radioactive disintegration chains of actinium, radium and thorium were known as:

• actinon or actinium emanation : ²¹⁹Rn
• thoron or thorium emanation : ²²⁰Rn
• radon or radium emanation, emanation, emanon, or niton : ²²²Rn

Table

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

• Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
• Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
• Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
  • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
  • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
  • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.