ABSTRACT
Isotopes are elements with unique atomic masses. That is, the isotopes of a given element have the same number of protons, but different numbers of neutrons. Stable isotopes are those isotopes of an element that have not been observed to radioactively decay. Most elements have more than one stable isotope. For example, hydrogen has two isotopes: 2H and 1H (often called deuterium and rarely protium, respectively), with the lighter isotope much more abundant than the heavier isotope. The average abundances of the common light stable isotopes that are of interest are shown in Table 10.1.
