Title: polarizability
Long Title: IUPAC Gold Book - polarizability
DOI: 10.1351/goldbook.P04711
Status: current
Index: quantity

Definition
The ease of distortion of the electron cloud of a molecular entity by an electric field (such as that due to the proximity of a charged reagent). It is experimentally measured as the ratio of induced dipole moment (\(\mu _{\mathrm{ind}}\)) to the field \(E\) which induces it: \[\alpha =\frac{\mu _{\rm{ind}}}{E}\] The units of \(\alpha \) are \(\rm{C}^{2}\ \rm{m}^{2}\ \rm{V}^{-1}\). In ordinary usage the term refers to the 'mean polarizability', i.e., the average over three rectilinear axes of the molecule. Polarizabilities in different directions (e.g. along the bond in $\ce{Cl2}$, called 'longitudinal polarizability', and in the direction perpendicular to the bond, called 'transverse polarizability') can be distinguished, at least in principle. Polarizability along the bond joining a substituent to the rest of the molecule is seen in certain modern theoretical approaches as a factor influencing chemical reactivity, etc., and parametrization thereof has been proposed.

Related Terms
- dipole moment: https://goldbook.iupac.org/terms/view/D01761
- electric polarizability: https://goldbook.iupac.org/terms/view/E01933
- molecular entity: https://goldbook.iupac.org/terms/view/M03986
- reagent: https://goldbook.iupac.org/terms/view/R05190

Source
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1151 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/P04711/html
- json: https://goldbook.iupac.org/terms/view/P04711/json
- xml: https://goldbook.iupac.org/terms/view/P04711/xml

Citation: Citation: 'polarizability' 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.P04711
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Accessed: 2026-05-10T09:20:04+00:00