The appropriateness of Pauling's theory as applied to ionic crystals and molecules has been investigated by considering alkali halides in particular. The properties considered are the cohesive energy, binding energy, vibrational frequency, rotational and vibrational constants, etc. The comparison of theory and experiment reveals that the theory is approximate because of the assumption of an over simplified potential form but is liable to yield better results if a variable value of the exponent of the inverse repulsive term is used instead of a constant value for all the alkali halides.