The electron is a negatively charged elementary particle. Its symbol is e. The alternative name Negatron is hardly used anymore.

In atoms and in ions electrons form the electron shell. Each of the bound electrons can be uniquely described by four quantum numbers (main quantum number, secondary quantum number, magnetic quantum number of angular momentum and spin quantum number) (Pauli principle). The free mobility of some of the electrons in metals is the reason for the electrical conductivity of metallic conductors.