Electron statistics describe the electron through a connected set of physical constants: mass, energy, charge response, magnetic behavior, and characteristic quantum lengths. The figures below come from the NIST CODATA 2022 constants table. Values marked as derived are conversions or calculations based on that same table, while the remaining figures are reported constants.
Contents
- Core electron measurements
- Mass, energy, and particle comparisons
- Charge and electromagnetic response
- Magnetic moment and g-factor
- Quantum length and scattering scales
- Atomic constants connected to the electron
- Thermodynamic and radiation constants
Core electron measurements
The electron is exceptionally light on the particle scale, but its mass can be expressed in several useful unit systems. NIST CODATA 2022 gives the electron mass as 9.109 383 7139(28) × 10−31 kg. In grams, the corresponding derived value is 9.109 383 7139(28) × 10−28 g. The same mass is 5.485 799 090 441(97) × 10−4 u, or about 0.0005485799090441 u.
That mass has a direct energy equivalent. NIST CODATA 2022 lists the electron energy equivalent as 0.510 998 950 69(16) MeV. Expressed as a derived energy in joules, the electron mass-energy is 8.187 105 7769(25) × 10−14 J. The corresponding rest-energy value per kilogram is 8.987 551 7923(28) × 10^16 J kg−1.
| Electron statistic | Value | Source label |
|---|---|---|
| Mass | 9.109 383 7139(28) × 10−31 kg | NIST CODATA 2022 constants table |
| Mass | 5.485 799 090 441(97) × 10−4 u | NIST CODATA 2022 constants table |
| Energy equivalent | 0.510 998 950 69(16) MeV | NIST CODATA 2022 constants table |
| Mass-energy | 8.187 105 7769(25) × 10−14 J | Derived from NIST CODATA 2022 constants table |
| Charge-to-mass quotient | −1.758 820 008 38(55) × 10^11 C kg−1 | NIST CODATA 2022 constants table |
The charge-to-mass quotient combines the electron’s electric charge with its mass. Its value is −1.758 820 008 38(55) × 10^11 C kg−1. The negative sign identifies the electron’s negative charge convention in this quotient. This statistic is especially useful when describing how an electron responds to electric and magnetic fields without separating the two underlying quantities.
Mass, energy, and particle comparisons
Comparisons with other particles put the electron’s small mass into context. The proton-to-electron mass ratio is 1836.152 673 426(32), while the electron-to-proton mass ratio is 5.446 170 214 889(94) × 10−4. These are reciprocal descriptions of the same mass contrast as reported in the NIST CODATA 2022 constants table.
The proton mass is 1.672 621 925 95(52) × 10−27 kg, its mass in atomic mass units is 1.007 276 466 5789(83) u, and its energy equivalent is 938.272 089 43(29) MeV. The neutron energy equivalent is 939.565 421 94(48) MeV, and the neutron-to-proton mass ratio is 1.001 378 419 46(40). The neutron mass is reported as 1.008 664 916 06(40) u.
The muon provides another comparison. Its mass is 0.113 428 9257(25) u, its energy equivalent is 105.658 3755(23) MeV, and the muon-to-electron mass ratio is 206.768 2827(46). NIST CODATA 2022 also gives the electron-muon mass ratio as 4.836 331 70(11) × 10−3.
Nuclear comparisons extend to the deuteron and helion. The deuteron mass is 2.013 553 212 544(15) u, its energy equivalent is 1875.612 945 00(58) MeV, and its deuteron-to-proton mass ratio is 1.999 007 501 2699(84). The helion mass is 3.014 932 246 932(74) u, with an energy equivalent of 2808.391 611 12(88) MeV. The constants table reports the electron-to-helion comparison using the electron mass entry divided by the helion mass entry, rather than as a separately simplified ratio.
Charge and electromagnetic response
The electron’s charge-to-mass quotient is one of its most recognizable electromagnetic statistics, but it sits within a broader group of constants. The fine-structure constant is 7.297 352 5643(11) × 10−3, and its inverse is 137.035 999 177(21). These dimensionless values characterize the strength of electromagnetic interaction in the constants framework.
The Faraday constant is 96 485.332 12 C mol−1. It links elementary charge to an amount of substance and is reported by NIST CODATA 2022 alongside particle and electromagnetic constants. The Bohr magneton is 9.274 010 0657(29) × 10−24 J T−1, or 5.788 381 7982(18) × 10−5 eV T−1. The nuclear magneton is much smaller at 5.050 783 7393(16) × 10−27 J T−1.
For particle-level magnetic comparisons, the proton magnetic moment is 1.410 606 795 45(60) × 10−26 J T−1, and the proton magnetic moment in nuclear magnetons is 2.792 847 344 63(82). The proton gyromagnetic ratio is 2.675 221 8708(11) × 10^8 s−1 T−1, while the shielded proton gyromagnetic ratio is 2.675 153 194(11) × 10^8 s−1 T−1. The proton magnetic shielding correction is 2.567 15(41) × 10−5.
Magnetic moment and g-factor
The electron magnetic moment is −9.284 764 6917(29) × 10−24 J T−1 according to the NIST CODATA 2022 constants table. In Bohr magnetons, it is −1.001 159 652 180 46(18). In nuclear magnetons, the value is −1838.281 971 877(32). The sign remains negative in each reported form, while the numerical scale changes with the magneton used for comparison.
The electron magnetic moment anomaly is 1.159 652 180 46(18) × 10−3. Its g-factor is −2.002 319 304 360 92(36), and the electron magnetic moment relative to the proton magnetic moment is −658.210 687 89(19). These figures show why the same magnetic property is commonly presented in multiple normalized forms: each representation highlights a different comparison scale.
The muon offers a related benchmark. Its magnetic moment is −4.490 448 30(10) × 10−26 J T−1, and its magnetic moment anomaly is 1.165 920 62(41) × 10−3. The electron and muon anomaly values are close in scale but are distinct reported constants, so they should not be treated as interchangeable measurements.
The deuteron magnetic moment is 4.330 735 087(11) × 10−27 J T−1, or 0.857 438 2335(22) nuclear magnetons. The neutron magnetic moment is −9.662 3653(23) × 10−27 J T−1, or −1.913 042 76(45) nuclear magnetons. The helion’s shielded magnetic moment is −1.074 553 110 35(93) × 10−26 J T−1, and its value in Bohr magnetons is −1.158 671 494 57(94) × 10−3.
Quantum length and scattering scales
Electron statistics also define characteristic length scales used in atomic and particle physics. The reduced Compton wavelength is 3.861 592 6744(12) × 10−13 m, while the full electron Compton wavelength is 2.426 310 235 38(76) × 10−12 m. The full wavelength is larger because it uses the unreduced form of the wavelength constant; the two values are therefore related but should be kept as separately named quantities.
The classical electron radius is 2.817 940 3205(13) × 10−15 m. It is a characteristic electromagnetic length, not a statement that the electron is a small classical solid sphere. The Thomson cross section is 6.652 458 7051(62) × 10−29 m2, giving an area scale for low-energy electromagnetic scattering.
The Bohr radius is 5.291 772 105 44(82) × 10−11 m. This scale is much larger than either Compton wavelength listed above and is used as a characteristic atomic length. Together, the reduced Compton wavelength, Compton wavelength, classical electron radius, Thomson cross section, and Bohr radius provide different ways to describe electron-related length and interaction scales.
Atomic constants connected to the electron
Several atomic constants in the NIST CODATA 2022 table are built around electron behavior. The Rydberg frequency is 3.289 841 960 2500(36) × 10^15 Hz, the Rydberg energy equivalent is 13.605 693 122 990(15) eV, and the Rydberg constant is 10 973 731.568 157(12) m−1.
The Hartree energy is 4.359 744 722 2060(48) × 10−18 J, or 27.211 386 245 981(30) eV. The Bohr radius and Hartree energy are complementary atomic scales: one expresses a characteristic distance and the other a characteristic energy. The table also lists the fine-structure constant and its inverse, which connect these atomic quantities to electromagnetic interaction strength.
These values are reported with uncertainty notation in parentheses. For example, 9.109 383 7139(28) × 10−31 kg communicates a central value followed by an uncertainty in the final shown digits. The notation is part of the reported statistic and should be retained when precision matters.
Thermodynamic and radiation constants
The same NIST CODATA 2022 constants table includes reference values that are useful when electron statistics are placed in broader laboratory contexts. The molar gas constant is 8.314 462 618 J mol−1 K−1. The molar volume of an ideal gas at 273.15 K and 101.325 kPa is 22.413 969 54 × 10−3 m3 mol−1.
Radiation-related constants include the Stefan–Boltzmann constant, 5.670 374 419 × 10−8 W m−2 K−4, and the Wien displacement law constant, 2.897 771 955 × 10−3 m K. These are not electron-specific measurements, but they appear in the same constants reference and provide useful unit and scale context for experimental physics.
Taken together, the electron’s mass, energy equivalent, charge-to-mass quotient, magnetic moment, quantum wavelengths, scattering area, and atomic constants form a compact numerical profile. The comparison values for protons, neutrons, muons, deuterons, and helions show how that profile relates to other particles and composite nuclei, while the thermodynamic and radiation constants anchor the measurements in wider physical-unit systems.