Electronvolt (eV)
Exactly 1.602176634×10⁻¹⁹ joules, the energy gained by an electron moving through one volt. Used in atomic and particle physics.
1 electronvolt = 1.602176634×10⁻¹⁹ joules (exactly).
About the electronvolt
Particle physicists adopted this unit because a charged particle crossing a voltage V gains energy qV, so an electron accelerated through one volt in a vacuum gains exactly one electronvolt. Since the 2019 revision of the SI, the elementary charge is fixed, which makes 1 eV exactly 1.602176634 x 10^-19 J. The NIST appendix page still shows a rounded, non-exact value, reflecting the time before this redefinition. The unit is not part of the SI itself.
It suits the atomic world. Visible photons carry roughly 1.65 to 3.26 eV, green light at 532 nm is about 2.33 eV, and ionising hydrogen needs 13.6 eV. Molecular bonds are on the order of 1 to 10 eV each, and thermal motion at 20 degrees Celsius corresponds to about 0.025 eV. Particle masses are also quoted in eV/c squared, so the proton is about 938 million of them. Larger multiples such as keV, MeV and GeV extend the scale upward.
Sources: Wikipedia: Electronvolt; NIST SP 811, Appendix B.8 (energy conversion factors)
Electronvolt conversion chart
1 electronvolt expressed in every other energy unit:
| Unit | 1 electronvolt |
|---|---|
| Joules | 1.602176634×10⁻¹⁹ |
| Kilojoules | 1.602176634×10⁻²² |
| Watt-hours | 4.45049065×10⁻²³ |
| Kilowatt-hours | 4.45049065×10⁻²⁶ |
| British Thermal Units | 1.518570443×10⁻²² |
| Calories | 3.829294058×10⁻²⁰ |
| Kilocalories | 3.829294058×10⁻²³ |
| Megajoules | 1.602176634×10⁻²⁵ |
| Gigajoules | 1.602176634×10⁻²⁸ |
| Megawatt-hours | 4.45049065×10⁻²⁹ |
| Foot-pounds | 1.181704842×10⁻¹⁹ |
| Millijoules | 1.602176634×10⁻¹⁶ |
| Kiloelectronvolts | 0.001 |
| Megaelectronvolts | 0.000001 |
| Gigaelectronvolts | 1×10⁻⁹ |
| Tons Of TNT | 3.829294058×10⁻²⁹ |
| Tonnes Of Oil Equivalent | 3.826733147×10⁻³⁰ |
| Therms | 1.518933028×10⁻²⁷ |
| Quads | 1.518570443×10⁻³⁷ |
| Ergs | 1.602176634×10⁻¹² |
| Calories (IT) | 3.826733147×10⁻²⁰ |
| Kilogram-force Meters | 1.63376549×10⁻²⁰ |
| Horsepower-hours | 5.968206271×10⁻²⁶ |
| Liter-atmospheres | 1.581225397×10⁻²¹ |
More Scientific units
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- ton of TNT (energy)
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