Electronegativity:  Chemical Hardness I

Abstract

It has been suggested that the absolute hardness of density functional theory be identified with the chemical hardness of Pearson's principle of hard and soft acids and bases. It is unclear whether these two hardnesses are actually equivalent and if not how they are related. The problems arising from the identification of chemical hardness with absolute hardness are examined, as well as the problems associated with the evaluation of absolute hardnesses. The nature of absolute hardness is explored in some detail which has given rise to an interpretation which is in conflict with the commonly accepted interpretations of chemical hardness.

Ultraviolet Absorption Spectra, Solvent Effect and Non-Linear Optical Properties of Tetrahydroxy-1,4-quinone Hydrate by Hartee-Fock and Density Functional Theory

“…Both HOMO and LUMO are the main orbitals that take part in chemical stability. The energy values of LUMO and HOMO and their energy gap determines the kinetic stability, chemical reactivity and, optical polarizability and chemical hardnesssoftness of a molecule [24]. The molecule has a large energy gap is known as hard and having a small energy gap is known as soft molecule.…”

Antiradical potential of phenolic compounds fingerprints of propolis extracts: DFT approach

“…In case of the electronegativity (v), high values imply a strong capacity to donate electrons. For hardness descriptor (g), high values indicate strong resistance to charge transfer, while low electrophilicity values (x), indicate a high capacity to donate electrons [47,50].…”

Evaluation of global hardness of atoms based on the commonality in the basic philosophy of the origin and the operational significance of the electronegativity and the hardness. Part I. The Gordy’s scale of electronegativity and the G.H.

“…Sen and Vinayagam [44] evaluated the density functional hardness of 12 elements only and the true density functional global hardness of the majority of atoms are still at large. Moreover, Reed [45] pointed out that the invocation of the finite difference approximation requires that the absolute hardness be essentially independent of charge over an interval of two units of charge. This does not appear to be the case of chemical hardness or absolute hardness.…”

“…We [46] also pointed out some inconsistency in the finite difference definition of hardness. Reed [45] has opined further that the operational definition contained in Eq. (6) and Eq.…”