Define the atomic mass unit.
One atomic mass unit is a mass unit equal to exactly one-twelfth ( 1 12th ) the mass of one atom of carbon 12 − . The relative atomic masses of all elements have been found with respect to an atom of carbon 12 − . According to the latest IUPAC (International Union of Pure and Applied Chemistry) recommendations, the atomic mass unit (written as ‘u’ – unified mass) is equal to the mass of one-twelfth ( 1 12th ) of carbon 12 − atom.
