Certain processes that are vital to life, including photosynthesis, combustion, and corrosion, fall into the class of reactions called oxidation–reduction, or redox, reactions. Redox reactions consist of two simultaneous processes: oxidation and reduction. Oxidation and reduction are complementary processes. In a redox reaction between two reactants, one reactant loses electrons and is oxidized, while the other reactant gains electrons and is reduced. Consider the oxidation–reduction reaction between potassium and chlorine. The neutral potassium atom loses an electron to become a potassium ion. Potassium is oxidized, and its charge increases from zero in the neutral atom to one-plus in the cation. The neutral chlorine atom gains an electron and becomes a chloride ion. Chlorine is reduced, and its charge decreases from zero in the neutral atom to one-minus in the anion. Since potassium donates an electron, it is the reducing agent, or reductant. Chlorine accepts the electron, so it is the oxidizing agent, or an oxidant. The redox process leads to the formation of potassium chloride.