In some chemical reactions, electrons are transferred from one substance to another, but there is no net gain or loss of electrons during the reaction. These reactions involve the oxidation, or loss of electrons, of one substance, and the reduction, or gain of electrons, of another. This type of reaction is called a redox reaction. In neutral atoms, such as A and X, the number of protons equals the number of electrons. When atom A loses an electron, the positive charge of the nucleus becomes greater than the negative charge of the electrons, and the resulting ion has a net positive charge, forming a cation. In a reaction, the electron must be taken up by another atom, X , which results in more electrons than protons and a net negative charge on the atom, forming an anion. Mnemonic devices can help in remembering the definitions of oxidation and reduction. Two common mnemonic devices are LEO (Losing Electrons: Oxidation) says GER (Gaining Electrons: Reduction), and OIL (Oxidation Is Losing) RIG (Reduction Is Gaining). Identify the equations that show the oxidation of neutral atom A and the reduction of neutral a