Title: resonance
Long Title: IUPAC Gold Book - resonance
DOI: 10.1351/goldbook.R05326
Status: current

Definition
In the context of chemistry, the term refers to the representation of the electronic structure of a molecular entity in terms of contributing structures. Resonance among contributing structures means that the wavefunction is represented by 'mixing' the wavefunctions of the contributing structures. The concept is the basis of the quantum mechanical valence bond methods. The resulting stabilization is linked to the quantum mechanical concept of 'resonance energy'. The term resonance is also used to refer to the delocalization phenomenon itself.

Related Terms
- contributing structures: https://goldbook.iupac.org//terms/view/C01309
- delocalization: https://goldbook.iupac.org//terms/view/D01583
- mesomerism: https://goldbook.iupac.org//terms/view/M03845
- molecular entity: https://goldbook.iupac.org//terms/view/M03986
- resonance energy: https://goldbook.iupac.org//terms/view/R05333
- valence: https://goldbook.iupac.org//terms/view/V06588

Source
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1161 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/R05326/html
- json: https://goldbook.iupac.org/terms/view/R05326/json
- xml: https://goldbook.iupac.org/terms/view/R05326/xml

Citation: Citation: 'resonance' 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.R05326
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-04-28T23:12:23+00:00