How are the radioactive decay of isotoped used to determine the age of rocks

Question

anonymous · Answer

Radioactive decay is a spontaneous process in which an isotope( the parent element) loses particles from it nucleus to form a new element( the daughter). The rate of decay is expressed in terms of the isotope's half-life - the period of time it takes for 1/2 of a particular radioactive substance to decay. Most have rapid rates of decay(short half-lives) and lose their radioactivity within a few days or years. Some isotopes, however, decay slowly and several are used as "geologic clocks".

anonymous · Answer

An example would be

Parent: Uranium - 238

Daughter: Lead - 206

Half Life Value: 4.5billion years