Natural isotopes, of which there
are about forty, end up transforming themselves into other isotopes
until they become a stable isotope of lead. All transmutations occur
because of alpha and beta emissions.
All the nuclei which procede from the initial one are called a radioactive series or radioactive
family.
Three radioactive series are known from natural isotopes: the thorium
series -4n-, the actinium series -4n+3- and the uranium series -4n+2- .
The following visual shows the uranium series. All the isotopes formed
have a mass number -A- given by the formula 4n+2, where n is a natural
number between 59 and 51. Check this for yourself.
The plutonium series -4n+1-, an example of an artificial
radioactive series, can be seen here.
