Isotopes of radon

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.

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
* "rooting" or "thorium emanation" : 220Rn
* "radon" or "radium emanation, emanation, emanon," or "niton" : 222Rn



* 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.


* 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.

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