Reduction

In-depth explanation of Reduction

Reduction is the gain of electrons by a species, which corresponds to a decrease in its oxidation number. In a half-reaction electrons appear as reactants, and the reduced species is the one that accepts electrons from another substance. Reduction and oxidation are inseparable, because every electron gained must have been lost by some other species. At an electrochemical cell, reduction occurs at the cathode. Understanding reduction is essential for interpreting the electrochemistry of metals and batteries.

Going deeper: Reduction

Key ideas: Reduction is gain of electrons, or decrease in oxidation number, with electrons on the reactant side: Cu2+ + 2e- giving Cu. In organic chemistry it also means gain of hydrogen or loss of oxygen. Reduction potentials measure the tendency of a species to be reduced; more positive E means easier reduction.

Common mistakes and connections: Students sometimes think the oxidation number goes up because reduction sounds like a gain of something; the number actually falls with electron gain. Another error is placing electrons on the wrong side. Reduction occurs at the cathode in every electrochemical cell, which links to electrolysis and cell design.

Visualization of Reduction

Silver ions gain electrons at the cathode and are reduced to silver metal, lowering their oxidation number from +1 to 0. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Copper ions are reduced: Cu2+ + 2e- -> Cu, and the oxidation number falls from +2 to 0.

Where Reduction fits in Acids, Bases & Electrochemistry

Reduction is topic 37 of 105 in Acids, Bases & Electrochemistry.

Related topics

• Blood Buffer SystemAdvanced
• Oxidation NumberBeginner
• OxidationBeginner
• Redox ReactionsBeginner
• Oxidizing AgentBeginner
• Reducing AgentBeginner

Browse all 105 topics in Acids, Bases & Electrochemistry