The electronic properties viz. bond ionicity and heat of formation of A^IB^IIIC₂^VI ternary semiconductor compounds with chalcopyrite structure are investigated using Phillips and Van-Vechten's dielectric theory^27-29 of solids. The values of homopolar energy gap, heteropolar energy gap and average energy gap have been evaluated for these materials. Using these parameters, Phillips ionicity of the bonds AC and BC is evaluated and is used to determine the heat of formation (-DH_f) for these materials. The presently investigated values of (-DH_f) are found in good agreement with the experimental data and reported literature values.