In chemistry or physics, abundance or natural abundance refers to the amount of a chemical element isotope existing in nature. The abundance of an isotope on the Earth may vary depending on the place, but remains relatively constant in time (on a short-term scale). In a chemical reaction, the reactant is in abundance when the quantity of a substance is enough (or high) and constant during the reaction. Relative abundance represents the percentage of the total amount of all isotopes of the element. The relative abundance of each isotope in a sample can be identified using mass spectrometry.
- Masterton, William L.; Hurley, Cecile N. (2008). Chemistry: Principles and Reactions (6 ed.). Cengage Learning. ISBN 0-495-12671-3