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  • Word comparison: atomic mass vs. atomic number

atomic mass vs. atomic number

atomic mass

noun

Chemistry.

  1. the mass of an isotope of an element measured in units formerly based on the mass of one hydrogen atom taken as a unit or on 1/16 (0.0625) the mass of one oxygen atom, but after 1961 based on 1/12 (0.0833) the mass of the carbon-12 atom.

atomic number

noun

  1. the number of positive charges or protons in the nucleus of an atom of a given element, and therefore also the number of electrons normally surrounding the nucleus. at. no.; Z