electron volt (eV)
An electron volt (eV) is a unit of energy equal to the amount of kinetic
energy an electron gains after being accelerated
through an electric potential of 1 volt in
a vacuum. The electron volt is about 1.60219 × 10-19 joules.
The electron volt can also be used as a unit of mass by applying Einstein's relation E = mc2. For example, the mass of the proton is 938.256 × 106 eV (938.256 MeV).
Chemically, for 1 mole of electrons 1 eV ~ 100 kJ mol-1 (96.49 kJ mol-1).
One electron volt is roughly half the energy carried by a single photon of red light. The minimum amount of energy needed to ionize hydrogen from its ground state is 13.6 eV.
The larger units MeV (= 106 eV), GeV (= 109 eV), and TeV (= 1012 eV) are also used.