Atomic weight

Figure 1. The atomic weight of an element is shown on the periodic table below its abbreviation.[1]

Atomic weight, or relative atomic mass, is a unitless number defined as the ratio of the average atomic mass of a given element to the atomic mass unit.[2] When multiplied with the molar mass constant, 1 g/mol, the atomic weight gives the molar mass of an element or molecule.


  1. Wikimedia commons [Online], Available:
  2. IUPAC, relative atomic mass (atomic weight) Ar [Online], Available:

Authors and Editors

Jordan Hanania, Kailyn Stenhouse, Jason Donev