Standard electrode potential

Standard electrode potential is the potential difference of a half-cell relative to the standard hydrogen electrode under specified standard conditions. It indicates a species’ tendency to gain or lose electrons.

Standard hydrogen electrode: A reference electrode assigned a potential of zero volts under standard conditions. Its assigned zero defines every standard electrode potential.
Cell potential: The voltage difference between the two electrodes of an electrochemical cell. Subtracting standard half-cell potentials gives a standard cell potential.
Oxidation–reduction reaction: A chemical reaction in which electrons move between species, changing their oxidation states. Each electrode potential describes one side of an electron-transfer reaction.
Formal potential: An effective electrode potential defined for specified solution conditions, including ionic strength and complexation. Unlike a standard potential, it can incorporate the actual chemical environment of an experiment.
Nernst equation: An equation relating electrode potential to standard potential, temperature, and reaction composition. It calculates how a half-cell potential changes away from standard conditions.
Galvanic cell: An electrochemical cell that generates electrical energy from a spontaneous redox reaction. Positive standard cell potential indicates a spontaneous galvanic reaction under standard conditions.
Half-reaction: A representation of either the oxidation or reduction part of a redox reaction. Tables list potentials for balanced half-reactions rather than complete cell reactions.
Open-circuit potential: The potential of an electrode or cell when no net current flows. It is measured in a particular system, not necessarily under standard conditions.
Electrochemical cell: A system in which redox reactions produce or use electrical energy through separated half-reactions. A standard potential becomes a cell voltage when paired with another half-cell.
Electrolysis: The use of electrical energy to drive a nonspontaneous chemical reaction. Potential data help determine the minimum voltage needed to drive a redox change.

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