A reducing agent is a chemical with electrochemical potential. It has an excess of electrons and is thus liable to undergo the process of oxidation and consequently, through the donation of electrons, cause substances in contact with it to reduce. Chemicals in a reduced state, which possess electrons, are in a higher energy level than those in an oxidized state. For example, the oxidized state of iron is rust (Iron II Oxide), the reduced state is the metal. Oxidation and reduction (the first syllables of which constitute the name for this type of reaction: redox) play a vital role in batteries, electroplating systems, and numerous other applications. All batteries rely on two electrodes, one of which reduces and one of which oxidizes. The movement of electrons between the two forms an external circuit which can be used to drive electronic devices. In electroplating processes, an electrolytic cell is used to deposit the positively charged ions of a metal onto a piece of another metal. Since the positive ions are attracted to the negative metal, it can be considered a reducing agent.