| Oxidation | Reduction | |
| Definition | Oxidation involves the loss of electrons by an atom, ion, or molecule. It results in an increase in the oxidation state or charge of the species. | Reduction involves the gain of electrons by an atom, ion, or molecule. It leads to a decrease in the oxidation state or charge of the species. |
| Electrons | In oxidation, electrons are on the “losing” side; they are removed from the species undergoing oxidation. | In reduction, electrons are on the “gaining” side; they are added to the species undergoing reduction. |
| Oxidation State | The oxidation state of the species increases during oxidation. | The oxidation state of the species decreases during reduction. |
| Half-Reaction | In a half-reaction, oxidation is represented as the loss of electrons (e.g., Fe → Fe^3+ + 3e^-). | In a half-reaction, reduction is represented as the gain of electrons (e.g., O2 + 4e^- → 2O^2-). |
| Oxygen/Hydrogen Rule | Oxidation often involves a species losing hydrogen atoms or gaining oxygen atoms. | Reduction often involves a species gaining hydrogen atoms or losing oxygen atoms. |
| Reaction Partner | Oxidation always occurs with a corresponding reduction reaction. | Reduction always occurs with a corresponding oxidation reaction. |
| Importance | Oxidation-reduction (redox) reactions are vital in various natural processes, including energy production, corrosion, and cellular respiration. | Redox reactions play a significant role in chemical reactions, energy storage, and biological processes, such as photosynthesis. |
| Example | When iron reacts with oxygen to form rust (iron oxide), iron loses electrons (oxidation). | When hydrogen reacts with oxygen to form water, oxygen gains electrons (reduction). |
