Atomic mass unit. a mass unit equal to exactly one-twelfth the mass of a carbon-12 atom.
atomic mass units; see atomic mass.
Atomic mass unit. Protons and neutrons each weigh about one atomic mass unit. The atomic mass unit is defined as exactly 1/12th the mass of a carbon-12 atom, or 1.66057 x 10 -24 g. Atomic mass units allow for determination of relative atomic masses of atoms for different elements.
atomic mass unit. the unit of mass appropriate to the nucleus of an atom, equivalent to 1/12 of the mass of the carbon nucleus.