Palmer, Fred L. Lightning Research Center, Osram Sylvania, Beverly, Massachusetts.
Pritchard, David E. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts.
Last reviewed:October 2019
- Measurement of atomic masses
- Single-ion mass measurements
- Determination of α
- Redefinition of kilogram
- Related Primary Literature
- Additional Reading
The mass of an atom or molecule on a scale where the mass of a carbon-12 (12C) atom is exactly 12.0 atomic mass units. The mass of any atom is approximately equal to the total number of its protons and neutrons multiplied by the atomic mass unit, u = 1.6605389 × 10−24 gram. (Electrons are much lighter, about 0.0005486 u.) No atom differs from this simple formula by more than 1%, and stable atoms heavier than helium all lie within 0.3%. See also: Atomic mass unit
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