electron volt

A unit of energy, equal to the amount of kinetic energy acquired by an electron accelerated by passing through a potential difference of one volt, determined experimentally to be about 1.602 176 × 10⁻¹⁹ joules. For a more precise value, consult the most recent CODATA table. Symbol, eV, but ev was used earlier². The unit was introduced in 1912¹ as the “equivalent volt”.

The electron volt is often used to express the mass of atomic particles, which is possible through Einstein’s famous equation expressing the equivalence of mass and energy, e = mc². One electron volt of energy is equivalent to about 1.073 544 × 10⁻⁹ unified atomic mass units.

Although the electron volt is not an SI unit, the SI prefixes are used with it. The prefix B (for billion, American style) has also been used, but it was deprecated by the IUPAP and is not currently in use.

1. O. W. Richardson and K. T. Compton.

Philosophical Magazine, volume 24, page 583 (1912).

2. National Research Council.
A Glossary of Terms in Nuclear Science and Technology.
New York: American Society of Mechanical Engineers, 1955.

Pages 56 and 59.