An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge. These charged particles are fundamental components of physical chemistry, playing crucial roles in the conductivity of solutions and the formation of ionic chemical bonds. The movement of ions through a substance, such as an aqueous solution or solid electrolyte, constitutes an electric current. In biological systems, the movement of specific ions across cellular membranes generates potential differences necessary for nerve transmission and metabolic processes. The stability and reactivity of an ion are determined by its charge and the electron configuration of the parent atom.