OIL RIG

Summary: OIL RIG is the mnemonic for redox reactions: Oxidation Is Loss of electrons; Reduction Is Gain of electrons. It tells you which side electrons appear on in half equations. Tags: igcse chemistry redox mnemonic keyword Created: 2026-07-14 Last Updated: 2026-07-14

OIL RIG is the essential IGCSE mnemonic for remembering the electron-transfer definitions of the two halves of a redox reaction: Oxidation Is Loss (of electrons), and Reduction Is Gain (of electrons). This mnemonic directly informs the construction of half-equations — when a species is oxidised, electrons appear on the product side (e.g., Mg → Mg²⁺ + 2e⁻), and when a species is reduced, electrons appear on the reactant side (e.g., Cu²⁺ + 2e⁻ → Cu). An equally popular alternative taught in many classrooms is LEO says GER (Loss of Electrons is Oxidation; Gain of Electrons is Reduction), which conveys the same logic in a different form. OIL RIG also helps identify the reducing and oxidising agents in a reaction: the substance that loses electrons (is oxidised) acts as the reducing agent, while the substance that gains electrons (is reduced) acts as the oxidising agent — a distinction that IGCSE candidates frequently confuse. In electrochemistry, OIL RIG maps onto electrode processes: oxidation always occurs at the anode and reduction at the cathode, so remembering which process involves electron loss pinpoints the anode even in unfamiliar cell diagrams.

Key term — IGCSE Chemistry (0620/0971) glossary.