Chemistry 30 Diploma Practice Exam 2026 - Free Chemistry Diploma Practice Questions and Study Guide

Gain of electrons is reduction. In redox chemistry, reduction means that a species gains electrons, which lowers its oxidation state (becomes more negative). For example, Fe3+ gaining an electron to become Fe2+ decreases the oxidation number from +3 to +2. The opposite process, oxidation, is loss of electrons and increases the oxidation state. Redox describes the overall oxidation–reduction couple, where one species is oxidized and another is reduced. Spontaneous refers to whether a process occurs without external energy, not to electron transfer itself.