Paulings Definition of Electronegativity

Pauling recognised that fKAB is an additive quantity in the sense that for example J HCI = JAff/ + /Ajci.  

This implies that A ab corresponds to the square of the difference of atomic properties, i.e. the atomic electronegativity values 

Having a method to determine relative electronegativities for the elements using molecular thermochemical data required the choice of an origin in order to obtain 

The determination of electronegativity values for the majority of the atoms, using eqs. (2.1 and 2.2), turned out to be difficult. Frequently the homonuclear dissociation energies Daa were not known and the Dab values had to be derived from atomisation energies, using the heats of formation of complex molecules. Several authors mastered these difficulties, 10], In particular the exhaustive treatment of Huggins[ll] deserves credit. 

To discuss all the numerous suggestions for the definition and use of electronegativity in detail is next to impossible. In lieu of this, we quote for the reader a sentence from Pauling s introduction to the original edition in 1939 of The Nature of the Chemical Bond [5]. He wrote then  

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Heats of formation can be derived by reversing the Pauling definition of electronegativity, but empirical corrections are needed to allow for extra strength of multiple oxygen or nitrogen bonding, as in... 

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