electronvolt
Non-SI unit accepted for use with SI
| Name | Symbol | Quantity | Value in SI units | |
| electronvolt | eV | energy | 1.602 176 634 × 10−19 J |  |
DefinitionThe electronvolt, symbol eV, is a non-SI unit of energy accepted for use with the SI. One electronvolt is equal to the kinetic energy acquired by one electron in passing through a potential difference of one volt in vacuum. The value of one electronvolt in terms of joules is found by multiplying the magnitude of the charge carried by one electron, expressed in coulombs, by one volt. The magnitude of the charge on one electron is equal to the elementary charge, e, which is defined as 1.602 176 634 × 10−19 C. Therefore, 1 eV = 1.602 176 634 × 10−19 J. |
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The electronvolt is often combined with the SI prefixes, and is typically used to measure the energies of elementary particles.
Unit of mass
Since mass is related to energy through Einstein’s mass-energy equivalence equation, E = mc2, the masses of elementary particles can be expressed in terms of electronvolts, and c, where c is the speed of light in vacuum.
Examples of masses of elementary particles
Quarks
| Name | Mass in MeV/c2 | Mass in SI units |
| up | 2.2 | 3.92 × 10−30 kg |
| down | 4.6 | 8.2 × 10−30 kg |
| charm | 1 280 | 2.28 × 10−27 kg |
| strange | 96 | 1.71 × 10−28 kg |
| top | 173 100 | 3.086 × 10−25 kg |
| bottom | 4 180 | 7.45 × 10−27 kg |
Leptons
| Name | Mass in MeV/c2 | Mass in SI units |
| electron | 0.511 | 9.109 × 10−31 kg |
| muon | 105.658 | 1.883 52 × 10−28 kg |
| tau | 1 776.86 | 3.167 54 × 10−27 kg |
Bosons
| Name | Mass in GeV/c2 | Mass in SI units |
| W boson | 80.385 | 1.432 992 × 10−25 kg |
| Z boson | 91.1875 | 1.625 565 × 10−25 kg |
| Higgs boson | 125.09 | 2.229 932 × 10−25 kg |
Metric System 