On the basis of a previously suggested approach to the calculation of 'inductive' electronegativities of atoms and groups a simple method of theoretical estimation of in situ inductive electronegativities is elaborated. The method also allows the determination of inductive local and global chemical hardness parameters on the basis of geometric characteristics of bonded atoms. This made it possible to provide a new 'steric' interpretation for some known chemical rules, such as the principle of maximum hardness. (C) 2000 Elsevier Science B.V