Electronegativity and the Bond Triangle

The dependence of bond type on two parameters, electronegativity difference (Δχ)and average electronegativity (χav), is examined. It is demonstratedthat ionic character is governed by the partial charges of the bonded atoms,and metallic character by the HOMO–LUMO band gap. Each of these dependsin a different way on both χ and χav, and the nature of thedependence allows rationalization of the variation of bond type. For compoundswith other than 1:1 stoichiometry it is shown that weighted average electronegativity—definedfor AnBm as (nχA + mχB)/(n + m)—allowsdistinction between compounds of the same elements and is a more appropriateparameter to use. The position of a binary compound in the bond triangle givesa good indication of the predominant type of bonding, although most bonds areintermediate between ideal types.