Part II M ost of the chronometric dating methods in use today are radiometric . That is to say, they are based on knowledge of the rate at which certain radioactive isotopes decay or the rate of other cumulative changes in atoms resulting from radioactivity.
Isotopes are specific forms of elements.
The various isotopes of the same element differ in terms of atomic mass but have the same atomic number. T he decay of radioactive elements occurs at different rates, depending on the specific isotope. These rates are stated in terms of half-lives . One half-life is the amount of time required for of the original atoms in a sample to decay. Over the second half-life, of the atoms remaining decay, which leaves of the original quantity, and so on.