AbstractThe geometries of molecules H3AXAH3(X=O, S, Se and A=C, Si) have been optimized using STO‐3Gab initiocalculations and gradient method and the results are in good agreement with reported experimental values. From the STO‐3G optimized geometries, we have also calculated the electronic structures of these molecules using 4–31G and 6–31G basis sets to obtain the MO energies, atomic net charges and dipole moments. The ionization potentials calculated by 6–31G basis set are in good agreement with experiment