Concept introduced by L. Pauling as the @[email protected] of an atom to attract electrons to itself. There are several definitions of this quantity. According to Mulliken it is the average of the @[email protected] and @[email protected] of an atom, but more frequently a relative scale due to Pauling is used where dimensionless relative electronegativity differences are defined on the basis of @[email protected] energies, \(E_{\text{d}}\), expressed in electronvolts: \[\chi _{\text{r}}\left(\text{A}\right)- \chi _{\text{r}}\left(\text{B}\right)=\left(\text{eV}\right)^{-\frac{1}{2}}\ \sqrt{E_{\text{d}}\left(\text{AB}\right)- \frac{1}{2}\ [E_{\text{d}}\left(\text{AA}\right)+E_{\text{d}}\left(\text{BB}\right)]}\] The scale is chosen so as to make the relative electronegativity of hydrogen \(\chi _{\text{r}} = 2.1\). The sign of the square root was chosen intuitively by Pauling.
Green Book, 2nd ed., p. 20 [Terms] [Book]
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1111 [Terms] [Paper]