ABSTRACT
Recognition that there is signicant charge separation in many molecules has a long history, as do efforts to make this charge separation more predictable. Thus, the concept of electronegativity can be traced back at least to Berzelius in 1835 [1,2]. Perhaps the best known electronegativity scale is that of Pauling [3,4], who assigned relative values to atoms on the basis of the estimated ionic characters of heteronuclear covalent bonds formed by these atoms. Pauling gave his electronegativities to only two signicant gures, which is realistic and appropriate for such an inherently approximate concept, but they have been and continue to be quite useful from a practical standpoint.
