Relative atomic mass

Relative atomic mass

1. Atoms are tiny so the mass of an atom is measured in a.m.u (atomic mass units).

2. The masses of all atoms are relative to the mass of carbon 12, which is taken as exactly 12.

3. Relative atomic mass = mass of one atom of an element/ 1/12 mass of one atom of carbon-12

4. Relative atomic masses are measured using a mass spectrometer and are shown in the periodic table as the larger of the two numbers associated with each element.

5. Definition: Relative atomic mass (Ar or RAM) is the weighted mean of masses of all isotopes of an element relative to one atom of carbon-12.

6. Definition: Relative molecular mass (Mr or RMM) is the weighted mean of mass of a molecule relative to one atom of carbon-12.