Title: electronegativity
Long Title: IUPAC Gold Book - electronegativity
DOI: 10.1351/goldbook.E01990
Status: current

Definition
Concept introduced by L. Pauling as the power of an atom to attract electrons to itself. There are several definitions of this quantity. According to Mulliken it is the average of the ionization energy and electron affinity 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 bond dissociation energies, \(E_{\rm{d}}\), expressed in electronvolts: \[\chi _{\rm{r}}\left(\rm{A}\right)- \chi _{\rm{r}}\left(\rm{B}\right)=\left(\rm{eV}\right)^{-\frac{1}{2}}\ \sqrt{E_{\rm{d}}\left(\rm{AB}\right)- \frac{1}{2}\ [E_{\rm{d}}\left(\rm{AA}\right)+E_{\rm{d}}\left(\rm{BB}\right)]}\] The scale is chosen so as to make the relative electronegativity of hydrogen \(\chi _{\rm{r}} = 2.1\). The sign of the square root was chosen intuitively by Pauling.

Related Terms
- bond dissociation: https://goldbook.iupac.org//terms/view/B00698
- electron affinity: https://goldbook.iupac.org//terms/view/E01977
- ionization energy: https://goldbook.iupac.org//terms/view/I03199
- power: https://goldbook.iupac.org//terms/view/P04792

Sources
- Green Book, 2nd ed., p. 20 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1111 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/E01990/html
- json: https://goldbook.iupac.org/terms/view/E01990/json
- xml: https://goldbook.iupac.org/terms/view/E01990/xml

Citation: Citation: 'electronegativity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.E01990
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Accessed: 2026-06-09T19:02:41+00:00