Isotope geochemistry

Abstract

Isotopes are atoms that belong to the same element, but have different numbers of neutrons. For example, hydrogen can have 0 neutrons (protium) or 1 neutron (deuterium) or 2 neutrons (tritium). The mass changes because of the extra neutrons, so protium hydrogen, with only a proton, has an atomic mass of about 1 amu (atomic mass unit), deuterium hydrogen, with one proton and one neutron, has a mass of about 2 amu and tritium, with one proton and two neutrons, is about 3 amu. Remember – if you change the number of protons, you change the element.