How do oxidation and reduction occur together in a redox reaction?

In an oxidation-reduction (redox) reaction, oxidation and reduction are inherently coupled processes that occur simultaneously. This reciprocity ensures that whenever one substance is oxidized, another is necessarily reduced.1

The fundamental mechanism behind this coupling is the transfer of electrons. During a redox reaction, a reducing agent gives up one or more electrons, thereby increasing its oxidation number (oxidation), while an oxidizing agent accepts those same electrons, decreasing its oxidation number (reduction).23

This relationship can be formally analyzed using the concept of half-reactions. Every redox reaction can be broken down into two complementary half-reactions:3
* Oxidation half-reaction: Shows the loss of electrons.3
* Reduction half-reaction: Shows the gain of electrons.3

When these two half-reactions are combined, the electrons must cancel out, reflecting the fact that the electrons lost by the reducing agent are the exact electrons gained by the oxidizing agent. While some reactions involve the transfer of oxygen or hydrogen atoms, these processes are also governed by the same electron-transfer principle, as the shifting of these atoms results in a net change in the oxidation states of the participating species.314