Free Radical Definition

Chemistry Glossary Definition of Free Radical

Diagram of free radical

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An atom or molecule with an unpaired electron. Because they have a free electron, such molecules are highly reactive.


Singlet oxygen, molecules with a free hydroxy group (-OH)


Free radicals are capable of starting rapid chain-reactions that destabilize the ions in other nearby molecules generating more free radicals.

In biological systems, free radicals are deactivated by anti-oxidants, uric acid, and certain enzyme activities.