Term: radical ion
https://doi.org/10.1351/goldbook.R05073

Definition:
A radical that carries an electric charge. A positively charged radical is called a 'radical cation' (e.g. the benzene radical cation C6H6·+); a negatively charged radical is called a 'radical anion' (e.g. the benzene radical anion C6H6·āˆ’ or the benzophenone radical anion Ph2Cā€“O·āˆ’). Commonly, but not necessarily, the odd electron and the charge are associated with the same atom. Unless the positions of unpaired spin and charge can be associated with specific atoms, superscript dot and charge designations should be placed in the order ·+ or ·āˆ’ suggested by the name 'radical ion'. (e.g. C3H6·+ ).

Note: In the previous edition of this Compendium, it was recommended to place the charge designation directly above the centrally placed dot. However, this format is now discouraged because of the difficulty of extending it to ions bearing more than one charge, and/or more than one unpaired electron. In mass spectroscopic usage the symbol for the charge precedes the dot representing the unpaired electron.

Related Terms:
1) electric charge (http://doi.org/10.1351/goldbook.E01923).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1156 (https://doi.org/10.1351/pac199466051077)

Citation: 'radical ion' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.R05073

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