A molecule is represented by using symbols of elements present in it. This representation is called molecular formula of the compound. Thus, a molecular formula of a substance tells us how many atoms of each kind are present in one molecule. In Figure, you will find that atoms in a molecule are not only connected in definite ways but also exhibit definite spatial arrangements. Properties of molecules depends upon the ways atoms are connected and on spatial configuration of the molecules. CO₂ and H₂O both are triatomic molecules but they have entirely different properties. CO₂ is a linear molecule and is a gas but H₂O is a bent molecule and a liquid. Sodium chloride (common salt) contains equal number of sodium and chlorine atoms and is represented by the formula, NaCl. Sulphuric acid, H₂SO₄ contains three elements : hydrogen, oxygen and sulphur.