what is atom?

gram atomic mass

Average atomic mass

heteroatomic molecule

How relative molecular mass is uptained?

Atom is the smallest particle that takes part in a chemical reaction.

Relative Atomic Mass is only a ratio, so it has no unit. If the atomic mass of an element is expressed in grams, it is called as Gram Atomic Mass

The average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes.

The molecule that consist of atoms of different elements is called heteroatomic molecule.

The relative molecular mass is obtained by adding together the relative atomic masses of all the atoms present in a molecule.