How does electron transfer change the oxidation numbers of atoms?

In an oxidation-reduction reaction, the transfer of electrons directly dictates changes in the oxidation number of the participating atoms. Because an atom's oxidation number represents the number of electrons it can donate, acquire, or share during bond formation, the loss or gain of these electrons shifts its oxidation state.123

These changes follow a consistent pattern:

• Oxidation: This occurs when an atom loses electrons. As a result of this loss, the atom's oxidation number increases.12
• Reduction: This occurs when an atom gains electrons. As a result of this gain, the atom's oxidation number decreases.12

While redox processes can also be described through the transfer of oxygen or hydrogen atoms, these mechanisms are fundamentally equivalent to electron transfer. In all cases, the oxidation-state change provides a formal way to track the movement of electrons, confirming that oxidation and reduction are complementary processes where the electrons lost by one species are acquired by another.142