# Definition:Electron

## Electron

An electron is an elementary particle which contains a single unit of negative elementary electric charge.

### Charge

The electric charge on the electron is $-1.60217 \, 6634 \times 10^{−19}$ coulombs.

That is, a negative charge whose magnitude is the value of the elementary charge.

### Mass

The mass of the electron is approximately $9.10938 \, 370 \, 15(28) \times 10^{-31}$ kilograms.

The actual size of the electron is still unknown.

The current best estimate is that its radius has an upper limit of the order of $10^{-22}$ metres.

## Also see

• Results about electrons can be found here.

## Historical Note

The electron was discovered by Joseph John Thomson, who measured the Electron Charge to Mass Ratio in $1897$.

This happened as a result of several decades of work by many scientists.