Atomic volume may be defined as the volume occupied by one mole atoms of the element at its melting point in solid state. It is obtained by dividing the gram atomic mass of the element by its density.

Atomic volume decreases along the period, reaches a minimum in the middle and then starts increasing. This is due to the different packing arrangement of atoms in different elements in the solid state. For example, `P_4`, `S_8` etc.

In moving down the group atomic volume goes on increasing gradually.