Electronegativity average orbital

Table 2.2 shows the values of average orbital electronegativities for some oxides and hydroxides, calculated according to the equation 2.17. One... 

It was mentioned above that the concept of average orbital electronegativity is used to characterize acid-base properties. According to this concept, acidity increases with increasing the numerical value of electronegativity while the basicity decreases, correspondingly. 

We calculated the differences between average orbital electronegativities for some combinations of oxides listed in Table 3.1. The results are represented in Table 3.2. 

Figure 3.1. Correlation between Gibbs energies and differences of average orbital electronegativities of tbe initials oxides for the synthesis reactions of sulphates and silicates.

Viting L.M., Avvakumov E.G. About correlation between Gibbs energies and average orbital electronegativities of complex oxides. Zhum. Fis. Khim. 2001 75 1120-22. Avvakumov E.G., Kosova N.V. Fast propagating solid-state mechanochemical reactions. Sibir. Khim. Zhum. 1991 5 62-. ... 

Both orbitals are stabilized if the average electronegativity increases both destabilized if it decreases. If the average electronegativity remains constant, one orbital rises while the other one is lowered. 

The physical meaning of our final equation is best seen on eqn 39. The term containing w is essentially the self-energy correction introduced by Mulliken in his analysis of electronegativities to account for the average repulsion of electrons occupying the same orbital. In order to get an idea of the orders of magnitude, let us apply eqn 39 to a model computation of FeCO, made to compare the ClPSl results of Berthier et al. [11] with those of a simple orbital scheme. Consider one of the two x systems of FeCO, treated under the assumption of full localization (and therefore strict cr — x separation)... 

The recent interest in the exploration of electrocatalytic phenomena from first principles can be traced to the early cluster calculations of Anderson [1990] and Anderson and Debnath [1983]. These studies considered the interaction of adsorbates with model metal clusters and related the potential to the electronegativity determined as the average of the ionization potential and electron affinity—quantities that are easily obtained from molecular orbital calculations. In some iterations of this model, changes in reaction chemistry induced by the electrochemical environment... 

FIG. 11. Correlation between the tip height on top of an adsorbate, the atom electronegativity, and the atomic polarizability, which may be related to the average radius of the appropriate atomic orbital. Far from the adsorbate the tip-substrate separation corresponds to 7.45 A for a 10 MQ gap resistance. (From Ref. 70.)... 

The conjugated C-atoms of a fullerene respond to the deviation from planarity by rehybridization of the sp o and the p Jt orbitals, since pure p character of Jt orbitals is only possible in strictly planar situations ]56]. The electronic struchue of non-planar organic molecules has been analyzed by Haddon using the Jt orbital axis vector (POAV) analysis. For Cjq an average o bond hybridization of sp and a fractional s character of 0.085 (POAVl) or 0.081 (POAV2) was foimd ]59-63]. Consequently, the Jt orbitals extend further beyond the outer surface than into the interior of Cgg. This consideration implies, moreover, that fullerenes and, in particular, Cgg are fairly electronegative molecules [64, 65] since, due to the rehybridization, low-lying Jt orbitals also exhibit considerable s character. 

The discussion of metallic valence and of electron transfer from hyperelectronic elements to hypoelectronic elements for metals, both in bulk alloys and on surfaces, is complicated somewhat by the need for consideration of the effect of the metallic orbital. As pointed out earlier, the metallic orbital, 0.72 per atom, on average, is required for the unsynchronized resonance of valence bonds characteristic of metals. For example, tantalum is hypoelectronic and copper is hyperelectronic, and accordingly, electron transfer from copper to tantalum is expected, leading to an increase in valence for both Ta and Cu and to increased strength of bonds [29]. This increased strength of bonds shows up in bulk alloys as an effect independent of the electron transfer induced by difference in electronegativity. 

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