Pauling electronegativity values

Using die values of electronegativity, Pauling further suggested that die fractional ionic contribution to the bond energy (FIG) is related to the electronegativities jca and xq in the A-B molecule and given by... 

This was justified as follows. The energy required to take an electron from a neutral atom Y to a neutral atom Z is /Y — AZt whereas the energy cost to take an electron from a neutral atom Z to a neutral atom Y is Iz — Ay. Hence, the two atoms Y and Z would have an equal propensity for attracting electrons or equal electronegativity if /Y — Az = Iz — AY, that is if IY + Ay = Iz + Az. This is consistent with the Mulliken definition, eqn (3.35), the factor 1/2 being arbitrary. As can be seen by comparing the two different scales in Fig. 3.5, the Mulliken values are approximately 2.8 times the Pauling values. 

The Mulliken electronegativities have a good linear relationship with the Pauling values, and the former are usually adjusted for consistency... 

Table 7.2 Abbreviated table of electronegativities ( Pauling s values)...

Table 1.7 Pauling electronegativity (x ) values for the i - and / -block elements.

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