Molecular formula can also be termed as the chemical formula. It is the number of atoms present in each element in a molecule of a compound. For example, water’s molecular formula is H2O. That means, in its one molecule, the number of atoms of hydrogen and oxygen are two and one respectively.

Molecular formula can be derived from empirical formula by the periodical table. Empirical formula is the ratio of atoms of different elements in whole numbers. The first step is to take the empirical formula for example, take the empirical equation CH2Cl. In this case, atomic masses are as follows-C=12; H=1; Cl=35.5.the total mass of the formula=12+1+1+35.5=49.5. In the second step, the molecular weight is to be divided by the formula mass. Let the molecular weight be 148.5. It is to be divided by 49.5. We get 3. In the third and the final step, each element of empirical formula is to be multiplied by the whole number we get in step2 that is 3 in this case. Therefore we multiply 1 of C with 3 we get 3; multiply 2 of H with 3 we get 6; multiply 1 of Cl with 3 we get 3. Thus we derive our molecular formula from the empirical formula of CH2Cl as C3H6Cl3.