Radioactive dating is a method of dating rocks and minerals using radioactive isotopes.
This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
Radioactive decay is a natural process and comes from the atomic nucleus becoming unstable and releasing bits and pieces.
These are released as radioactive particles (there are many types).
This decay process leads to a more balanced nucleus and when the number of protons and neutrons balance, the atom becomes stable.
This radioactivity can be used for dating, since a radioactive 'parent' element decays into a stable 'daughter' element at a constant rate.
The rate of decay (given the symbol λ) is the fraction of the 'parent' atoms that decay in unit time.