According to Dalton, an atom is something that cannot be divided further. This is the ultimate particle of an element that maintains its chemical identity throughout all chemical and physical changes. Thus, the atoms are the building blocks of all matter.

A molecule is the smallest particle of a substance (element or compound) which is capable of independent existence and shows all the properties of that substance. A molecule may be regarded as a group of two or more atoms that are chemically bonded together.

Atomic mass of an atom is defined as 1 12 th of the mass of carbon- 12 atom. In other words, atomic mass expresses the number of times an atom of the element is heavier than a carbon atom whose atomic mass is taken as 12 u .

Calculate the molar mass of Sulphuric acid, H 2 SO 4 .

The gram atomic mass of sulphur= 32 g , The gram atomic mass of hydrogen= 1 g , The gram atomic mass of oxygen= 16 g . The molar mass of H 2 SO 4 = ( 2 × Gram atomic mass of H ) + Gram atomic mass of S + ( 4 × Gram atomic mass of O ) . The molar mass of H 2 SO 4 = 2 × 1 + 32 + ( 4 × 16 ) = 98 g .