A chemical formula is a notation used to convey the relative properties of the atoms of the different elements in a substance. The Chemical Formula of any compound should not be changed for the sake of convenience because each compound has a fixed chemical formula.A Chemical Formula shows the elements that make up the compound and the
numbers of atoms of each element in the smallest unit of that compound,
be it a molecule or a formula unit.
The elements symbol is required to write the chemical formula. Symbols for chemical element are taken from the periodic table.
The chemical formula for a substance shows its chemical composition as elements present and the ratio in which the atoms of the elements occur.