Electronegativity Scales And Their Applications

Electronegativity (EN),χ, is an important index to describe "the power of an atom in a molecule to attract electrons to itself" which is closely related with the detailed chemical environment of the atoms. Because the concept of EN is of simplicity and ease to use, it has been widely used as a basic atomic parameter to explain and predict various physicochemical properties and chemical phenomena.This thesis has three sections. Firstly, on the basis of average attractive energy of valence electrons, a new ionic gas-phase EN scale was defined, which was proved to be useful for the quantitative prediction of the Lewis acidity strength of the metal oxides. Secondly, the thesis focus on the solvent effect on the EN and proposed an EN scale of metal ions in aqueous solution with the most common oxidation states and hydration coordination numbers in terms of the effective ionic electrostatic potential. It is found that the metal ions in aqueous solution are poorer electron acceptors compared to those in the gas phase. This solution-phase EN scale shows its efficiency in predicting some important properties of metal ions in aqueous solution such as the aqueous acidities of the metal ions, the stability constants of metal complexes and the solubility product constants of the metal hydroxides. Moreover, the difference between the standard reduction potential and the solution-phase EN of metal ions was elaborated. Lastly, because the electroaccepting and electrodonating powers index are to describe the electro-accepting and electro-donating power of chemical systems as the concept of EN, and none has studied on the solvent effect on these indices, the solvent effect on the electroaccepting and electrodonating powers index was examined and the expression of electroaccepting and electrodonating powers in the solution phase was obtained. It was found that there exists a good relationship between these indices and our solution-phase EN.