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|
|Half life (yrs)||10|
|Half life (yrs)||13.5|
|Name of series||Thorium (Natural)||Neptunium (Artificial)||Uranium (Natural)||Actinium (Natural)|
|Number of lost particles|