Electronegativity and atomic charge

Abstract

The electron distribution is fundamental in determining chemical and physical properties of substances. In a very qualitative fashion electronegativity is used throughout the chemistry curriculum as an indicator of atomic charge-and thus electron distribution.Because electronegativity is a far more fundamental concept than previously thought, it should be continually developed in sophistication throughout the curriculum. However, after electronegativity is introduced in the first semester of the first course (1-3) little is done to develop the concept further(4-ft>). For example, electron distributions and bonding are covered in most physical chemistry texts, yet electronegativity, which is essential to these concepts, is all but neglected.The Value of the Quantitative Approach Unfortunately, the student's understanding of electronegativity remains very qualitative, and atomic charge discussions are subject to a great deal of hand-waving. Of course

Electronegativity: Chemical Hardness II

“…It is interesting to note that the donor atoms carry a very large range of charges, Table . It has been shown that donor atom charge correlates strongly with the overall strength of acids and bases, − but there is virtually no correlation with the operational hardness of these bases ( r = 0.263). There is a very large range in the ionicities of the bonds formed between the base and the discriminating acid.…”

“…Absolute Hardness and Electronegativity. The absolute hardnesses η and the electronegativities were obtained from the ionization data provided by Hinze and Jaffe. , The electronegativities used were those for the atoms in their appropriate valence states. The local hardness was taken to be that of the individual atoms, and to be approximately equal to that of the isolated gaseous atom in the appropriate valence state (2 η = b = IE − EA).…”

Comparative Studies on Thermal Decompositions of Dinitropyrazole-Based Energetic Materials

“…In this study, a standard of BO cutoff of 0.3 [26,27] was chosen, which means that the chemical bond between i and j atoms was formed if their bond level was greater than 0.3. EEM method [28] is applied to describe the charge of an atom in the calculations based on ReaxFF force field and the description of long-range interactions is added to ReaxFF-lg force field [29] for van der Waals forces. Isothermal-isobaric (NPT) MD simulation with a 0.25 fs time step is also applied to relax the internal stresses and obtain the initial structures of LLM-116 and LLM-226.…”

A quantum theory atoms in molecules investigation of Lewis base protonation

“…Reed showed that the atomic charge of the donor atom in a base is a “poor indicator of base strength” and much more reliable correlations between proton affinities and atomic charges are obtained if one uses instead the resulting charge values of the proton in the BH + cation . Proton affinities were also related to electronegativity values . According to Reed, the explanation to these tendencies lies on the charging energy, the energy amount needed to bring each atom to the charge it will eventually carry in the molecular system .…”

“…[17] Proton affinities were also related to electronegativity values. [18] According to Reed, the explanation to these tendencies lies on the charging energy, the energy amount needed to bring each atom to the charge it will eventually carry in the molecular system. [17] A further investigation also indicated that generalized atomic polar tensor (GAPT) charges [19] assumed by the proton provide better linear correlations with proton affinities than those given by the Mulliken method.…”