Radioactive Decay Series
A sequence of successive radioactive decays leading from a long-lived parent to a stable end product.
Unit
Dimensionless
In depth
Because alpha decay changes the mass number by four and beta decay not at all, every nuclide in a series has a mass number in the same family modulo four. Three natural series exist, all terminating in a stable isotope of lead.
Examples in the real world
Uranium-238 decaying through fourteen steps, including radon-222, to end as lead-206.