While the number of protons defines the element (e.g., hydrogen, carbon, etc.) and the sum of the protons and neutrons gives the atomic mass, the number of neutrons defines the isotope of that element ...

The weighted mean mass of chlorine is 35.5. The relative atomic mass of an element is a weighted mean mass of the isotopes of an element compared with that of the 12 C isotope, which has a mass of ...

This variation in the relative abundance of stable isotopes results from tiny mass differences that cause ... Deuterium (the heavy hydrogen isotope) has revolutionized stable isotope analysis ...