[bluegirl]

i don't know the different between atomic mass unit and relative atomic mass.

[Dan]

Relative atomic mass is measured in atomic mass units. So relative atomic mass is a measurement, atomic mass unit is just the unit that the measurement is expressed in. It's like the difference between length and metres, or mass and kilograms, or temperature and kelvin etc. etc.

[Donaldson Tan]

Relative Atomic Mass (RAM) is the ratio of the mass of an atom to 1/12 of the mass of the Carbon-12 atom. Relative Molecular Mass (RMM) is the ratio of the mass of an atom to 1/12 of the mass of the Carbon-12 atom.

The atomic mass unit (amu) is 1/12 of the Carbon-12 atom.

Hence, the mass of an atom is given by RAM*1amu, whereas the mass of a molecule is given by RMM*1amu