A chemical formula is a symbolic representation of the composition of a chemical compound or molecule. It uses the symbols of the elements that make up the compound and numbers (subscripts) to indicate the number of atoms of each element present in one molecule or formula unit.
In simpler terms:
Elements: The chemical formula lists the elements that are part of a compound.
Atoms: The numbers next to the element symbols (subscripts) tell you how many atoms of that element are in the compound.
Example: The chemical formula for water (H₂O) shows that it is made of hydrogen (H) and oxygen (O), and each water molecule contains two hydrogen atoms and one oxygen atom.