What is the Charge of One Electron?

The electric charge of a single electron is extremely small. It is denoted by the symbol e.

The accepted value is: e = −1.602 × 10⁻¹⁹ Coulombs (C)

• The negative sign (−) indicates that the charge is negative.
• A proton carries the exact same amount of charge, but positive (+1.602 × 10⁻¹⁹ C).
• Because the magnitude is the same, atoms with an equal number of protons and electrons are electrically neutral.

The magnitude 1.602 × 10⁻¹⁹ C is known as the Elementary Charge. It is considered the smallest possible discrete unit of electric charge that can exist freely in nature. All observable electrical charges in the universe are integer multiples of this number (e.g., you can have a charge of +1e, -2e, +3e, but never 1.5e). This concept is called the quantization of charge.

The electron itself was discovered by J.J. Thomson in 1897 using a cathode ray tube. However, Thomson could only measure the ratio of the electron's charge to its mass (e/m ratio), not the exact charge itself.

The exact charge was brilliantly measured by American physicist Robert A. Millikan in 1909 through his famous Oil Drop Experiment. By observing tiny electrically charged drops of oil floating between two metal plates, he was able to calculate the precise force acting on them and deduce the charge of a single electron.