Answer 1

A chemical formula is an expression that denotes the number and types of atoms present in a molecule of a substance. It is a representation of the composition of a molecule, in terms of the elements present, using their symbols.

For example: O₂ is the chemical formula of the element oxygen. Therefore, one molecule of oxygen comprises two atoms.

CO₂ is the chemical formula of the compound carbon dioxide. It consists of one atom of carbon and two atoms of oxygen.