Application of stable isotopes in analysis and metabolism

Abstract

Many of the elements in the periodic table consist of more than one isotope, i.e., chemically identical species with differing atomic masses. Most of these isotopes are not radioactive in their natural state and are referred to as stable isotopes. The element copper, for example, has an atomic number of 29 and an atomic weight of 63.5, and consists of two stable isotopes: ⁶³Cu and ⁶⁵Cu. The atomic nucleus of each contains 29 protons, but ⁶⁵Cu contains 2 more neutrons than ⁶³Cu in its nucleus. The 2 stable isotopes of copper have “atomic weights” of 63 and 65 and thus differ in mass while being chemically identical. Naturally occurring copper is about 69% ⁶³Cu and about 31% ⁶⁵Cu, resulting in the overall elemental atomic weight of 63.5.