# 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* = *mc*^{2}. For
example, the mass of the proton is 938.256 × 10^{6} 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 (= 10^{6} eV), GeV (= 10^{9} eV), and
TeV (= 10^{12} eV) are also used.