Question

The charge on the electron.

Answer 1

Electron:

The negatively charged particle that revolves in the shells of atom is known as an electron.

Charge on electron:

1. The charge on the electron was determined by oil drop experiment by R. A. Millikan.
2. The absolute charge on electron is $1$ coulomb of negative charge.
3. This suggests that an electron has $1$ unit of negative charge.

Thus, the charge on an electron is $-1$.