The paired transfer of electrons
Oxidation corresponds to electron loss and reduction to electron gain in a transfer description. The two balance within a complete reaction. An oxidizing agent accepts electrons and is reduced, while a reducing agent supplies them and is oxidized; their names describe effects on the other reacting species.
References: [1]
Oxidation numbers as accounting
Oxidation numbers assign bonding electrons by formal rules, allowing changes to be tracked even in covalent compounds. An increase indicates oxidation and a decrease reduction. These values need not equal actual local atomic charges, but help classify reactions and balance both atoms and overall charge.
References: [1]
Separating reactions at electrodes
A galvanic cell separates oxidation and reduction at different electrodes. Electrons travel through an external circuit, while ionic pathways maintain charge balance. Oxidation occurs at the anode and reduction at the cathode, connecting a spontaneous chemical transformation with electrical work delivered to surrounding equipment.
References: [2]
Energy flow in cells and electrolysis
Galvanic cells deliver electrical work through spontaneous reactions, whereas electrolysis receives external energy to drive conversion. Both involve electrode processes and charge accounting, with opposite energy roles. Materials, solvents and concentrations determine practical behaviour beyond what oxidation-number changes alone can establish about voltage or efficiency.