According to Dulong and Petit’s Law, the product of atomic weight and specific heat equals to 6.4
(Approx.). This law can be used to calculate exact atomic weight.
In this method equivalent weight and specific heat are determined experimentally. Then approx. atomic weight is calculated as:-
Approx. Atomic weight × Specific Heat = 6.4
Approx. Atomic Weight = 6.4/Specific Heat
Again,
Approx. Valency is calculated as:
Approx. Valency = Approx. Atomic Weight / Exact Weight
If Approx, Valency is in fraction, it is converted into whole number, which is exact valency.
Finally Exact Atomic Weight is calculated as:
Exact Atomic Weight = Exact Weight × Exact Valency
Q. Why mass number is always whole?
Mass number is the sum of proton and neutron, It is always whole number, because proton and neutron both are whole number.