Radioactive Disintegration Series

The phenomenon of natural radioactivity continues till stable nuclei are formed. All the nuclei from the initial element to the final stable element constitute a series known as disintegration series. Further we know that mass numbers change only when a-particles are emitted (and not when b-particles are emitted) causing the change in mass of 4 units at each step. Hence the mass numbers of all elements in a series will fit into one of the formulae. 4n, , and , hence there can be only four disintegration series.

	4n	4n + 1	4n + 2	4n + 3
	58	59	59	58
Parent element
Half life (yrs)		10
Half life (yrs)				13.5
Name of series	Thorium (Natural)	Neptunium (Artificial)	Uranium (Natural)	Actinium (Natural)
End product
	52	52	51	51
Number of lost particles