Uranium and Thorium decay chains.

The Actinide decay chains of relevance to natural radioactivity are tabulated with the principal nuclei in large print. Nuclei with equilibrium relative decay rates > 10 -4 are linked to details of half-life and decay scheme (energies, relative intensities).

Isotopes sufficiently long-lived that their selective enrichment or depletion in refining or other chemical processes leads to departures from equilibrium are shown on a yellow background, while radon isotopes (which may be present in air) are shown on cyan.