Electron mass

Electron mass is the electron’s invariant rest mass, approximately 9.109 × 10⁻³¹ kilograms. It also serves as a natural mass unit in atomic and particle physics.

Electron: The electron is a stable elementary particle with negative electric charge and spin one-half. Electron mass is the electron’s intrinsic rest-mass property.
Cyclotron frequency: Cyclotron frequency is the orbital frequency of a charged particle moving in a uniform magnetic field. Its dependence on charge-to-mass ratio enables electron-mass measurements.
Bohr radius: The Bohr radius is the characteristic length scale of the ground-state electron orbit in the hydrogen model. It depends directly on electron mass and sets the scale of atomic size.
J. J. Thomson: J. J. Thomson was a physicist who identified the electron in cathode-ray experiments in 1897. His measurements established the electron’s charge-to-mass ratio, not its mass alone.
Invariant mass: Invariant mass is a system’s mass measured in its center-of-momentum frame and unchanged by Lorentz transformations. The electron’s rest mass is its invariant mass.
Penning trap: A Penning trap confines charged particles using a static magnetic field and an electrostatic quadrupole field. Trapped electrons can be measured through their characteristic oscillation frequencies.
Rydberg constant: The Rydberg constant is a physical constant that sets the wavenumber scale of hydrogen spectral lines. Its theoretical value depends on electron mass and reduced mass.
Robert Millikan: Robert Millikan was an American physicist known for measuring the elementary electric charge with the oil-drop experiment. Combining his charge measurement with Thomson’s ratio yielded an estimate of electron mass.
Mass–energy equivalence: Mass–energy equivalence is the relation between a system’s mass and energy, expressed by E = mc². It converts the electron’s mass into its rest energy.
Charge-to-mass ratio: Charge-to-mass ratio is the electric charge of a particle divided by its mass. Combining the electron’s measured ratio with its charge gives its mass.

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