Bonding Strength and Valence Matching

The valence sum rule is not sufficient by itself to determine the valences of individual bonds, but the principle of maximum symmetry (1) implies that the bonds formed by an atom will have similar valences. In this case the valences of all the bonds in the coordination sphere are expected to be close to their average which can be calculated using Eq. (6) provided we know the number of bonds the atom forms. 

If the value of N is known or can be inferred from other considerations, this value should be used in Eq. (6). If N is not known, a standard value, Nq, the average of the observed coordination numbers with oxygen ligands, can be used as a best guess instead, as shown in Eq. (7) [15]. The resulting value of So is known as the bonding strength of the atom, since, in the absence of any better information, the bonds formed by the atom are expected to have valences close to So- 

The bonding strengths of many elements in the Periodic Table are shown in Tables 1-3. The bonding strength, which is characteristic of each atom type, has two important uses. Firstly, the bonding strengths, Se, of the different elements when in their highest valence state, Fmax i-e., when all the electrons in the 

Bonding strengths are calculated using Eq. (7) (except those in parentheses which are estimated) These cations are also found in lower oxidation states with one or more lone pairs Hydrogen has two bonding strengths (see Sect. 8.1.1) 

Anion bonding strengths are based on coordinatirai numbers of 4 for N, O and F, and 6 for Cl 

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