Term: reduced species
https://doi.org/10.1351/goldbook.R05219

Definition:
A term used to characterize the degree of reduction (or oxidation) in atoms, molecules and ions. An atom in a molecule or an ion which has a low oxidation state. An element or atom in a compound can be reduced by the reaction of an element or compound with hydrogen, while it can be oxidized by reaction with oxygen. A reduced species can be formed also through the gain of electrons (either at the negative electrode in a cell or through transfer from another atom, ion or group of atoms in a chemical reaction). For example, the carbon atom in CH4 and other hydrocarbons is in a reduced state, while the carbon in CO2 is in an oxidized state. Similarly the sulfur atom in H2S is in a reduced state while that in sulfuric acid (H2SO4) is in an oxidized state.

Related Terms:
1) oxidation (http://doi.org/10.1351/goldbook.O04362).
2) hydrocarbons (http://doi.org/10.1351/goldbook.H02889).
3) oxidation state (http://doi.org/10.1351/goldbook.O04365).

Source: PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2210 (https://doi.org/10.1351/pac199062112167)

Citation: 'reduced species' 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.R05219

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