Electronegativity scales and electronegativity-bond ionicity relations: A comparative study

Electronegativity (χ) and bond ionicity are very important concepts in chemistry and other branches of science. Due to the lack of a precise definition, several χ scales have been introduced, based on a variety of chemical and physical quantities. On the other hand, many empirical relations have been devised to estimate the bond ionicity from χ of the bonding atoms. In this work, the bond ionicity in an extensive list of ANB8−N compounds, obtained by employing the Abu-Farsakh and Qteish ionicty scale (qi), are used as a benchmark to investigate the performance of the widely accepted and promising χ scales and frequently adopted χ-ionicity relations. The employed ionicty scale is based on the centers of the maximally localized Wannier functions and has several advantages. It has been demonstrated that the bond ionicity is better expressed in terms of normalized Δχ, rather than Δχ, and the best χ-ionicity relation has been unambiguously identified. The Allred-Rochow (AR) electronegativity scale is found to outperform the other considered electronegativity measures. The discrepancies between qi and bond ionicity (pi), obtained by using the best χ-ionicity relation and the AR scale, are found to have clear trends, which may imply that the AR values of some atoms are inaccurate. Corrections to the AR values, to minimize the discrepancies between qi and pi, lead to a highly reasonable set of χ values of the involved atoms that satisfy the main χ rules.