Electron Mass

Rest mass of the electron, anchoring the size of atoms through the Bohr radius and Rydberg constant.

Specifications & Metrics

symbol

mₑ

status

Measured (CODATA 2022)

value

9.1093837139 × 10⁻³¹ ± 2.8 × 10⁻⁴⁰ kg

Relative Scale in Constants

Core Principles & Analysis

• Equals 9.109 × 10⁻³¹ kg, or 0.511 MeV/c² — the energy of each photon in electron-positron annihilation.
• The proton outweighs it 1836-fold, which is why nuclei sit nearly motionless while electrons form the atom.
• Enters the Bohr radius and Rydberg constant, so atomic sizes and spectra scale directly with it.

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