Sanderson’s electronegativity

These descriptors have been widely used for the past 25 years to study chemical reactivity, i.e., the propensity of atoms, molecules, surfaces to interact with one or more reaction partners with formation or rupture of one or more covalent bonds. Kinetic and/or thermodynamic aspects, depending on the (not always obvious and even not univoque) choice of the descriptors were hereby considered. In these studies, the reactivity descriptors were used as such or within the context of some principles of which Sanderson s electronegativity equalization principle [16], Pearson s hard and soft acids and bases (HSAB) principle [17], and the maximum hardness principle [17,18] are the three best known and popular examples. 

Table 1.6 Elemental properties first four ionization potentials (II, 12,13,14, from Samsonov, 1968 values expressed in eV values in parentheses are of doubtful reliability) electron affinity (e.a., from Samsonov, 1968 eV) Pauling s electronegativity (P, from Samsonov, 1968 eV) Sanderson s electronegativity (S, from Viellard, 1982 adimensional). 

The crudest one is Sanderson s electronegativity equalization principle [39, 40] according to which atoms-in-molecule make electron transfers from lower to higher electronegative parts thus achieving equilibrium in electronegativity. 

Just like Sanderson s electronegativity equalization principle, the Hard and Soft Acids and Bases principle was originally introduced without strong theoretical basis. Nevertheless, it was used widely from its formulation on. The principle states that hard acids prefer to coordinate with hard bases and soft acids with soft bases [82], In 1983, Parr and Pearson provided a definition for the chemical hardness [25]... 

It is commonplace among chemists to think of a molecule as formed from its constituent atoms and accordingly to try to relate molecular properties to respective atomie properties. For example, Sanderson s electronegativity equalization principle (EEP) states that molecular electronegativity (chemical poten-... 

FIGURE 3.3 Sanderson s electronegativity equalization principle. (Adapted from P. Geerlings and F. De ProfL Chemical Reactivity as Described by Quantum Chemical Methods. Int. J. Mol. Sci. 3, no. 4 (2002) 276-309.)... 

Tempted by the interpretation of the Kullback-Leibler expression (9.78) as a tool to distinguish two probability distributions, the possibility of using it to compare atomic density functions is explored. To make a physically motivated choice of the reference density Po x) we consider the construction of Sanderson s electronegativity scale [63], which is based on the compactness of the electron cloud. Sanderson introduced a hypothetical noble gas atom with an average density scaled by the number of electrons. This gives us the argument to use renormalized noble gas densities as reference in expression (9.78). This gives us the quantity... 

For the construction of the functional in the above section, the choice to set the reference (the prior) density to that of a hypothetical noble gas atom, in analogy to Sanderson s electronegativity scale, was motivated and the particular choice lead to results which could be interpreted chemically. Following these findings one can see that it would be interesting to compare the information entropy, evaluated locally as... 

Sanderson defined a scale of electronegativity [21] based on the assumption that the reactivity of an atom, i.e. its propensity to retain its own electrons and attract others, is linked to its compactness. The most inert elements, the rare gases, are the most compact. Therefore, a chemical combination is the result of the tendency of the atoms to attain the configuration of the most chemically inert elements. Sanderson s electronegativity is characterized by the stability ratio S, which is defined as the ratio of the compactness of an atom to that of the most inert (or compact) element / of its period—the rare gas S = D/D, with D = ZjV = 3Z/47rr. Here Z is the atomic number of the atom and r is the covalent radius. Sanderson s electronegativity is a dimensionless number. 

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