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  • Word comparison: atomic weight vs. mass number

atomic weight vs. mass number

atomic weight

noun

Chemistry.

  1. the average weight of an atom of an element, formerly based on the weight of one hydrogen atom taken as a unit or on 1/16 (0.0625) the weight of an oxygen atom, but after 1961 based on 1/12 the weight of the carbon-12 atom. at. wt.

mass number

noun

Physics.

  1. the integer nearest in value to the atomic weight of an atom and equal to the number of nucleons in the nucleus of the atom. A