Atomic mass

The atomic mass of an element is the microscopic mass of an element in atomic mass units.[1]

This means that different isotopes of an element have different atomic masses (for example 235U has a different atomic mass than 238U).

The atomic number, also known as the average mass, or atomic weight, is an average mass of a distribution of isotopes of the element. Because it is an approximation of this mass, it is roughly the sum of the number of protons and neutrons in an atomic nucleus.[1]

Careful measurements of the mass of individual atoms will yield an atomic mass. To learn more about atomic mass, and its units, check out hyperphysics or UC Davis' Chem Wiki.


Authors and Editors

James Jenden, Kailyn Stenhouse, Jason Donev