electron

electron (symbol e) Stable elementary particle with a negative charge (−1.602 × 10⁻¹⁹C), a rest mass of 9.1 × 10⁻³¹ kg and a spin of Aw fermion. J. J. Thomson first identified electrons in 1897. They are not made up of smaller particles and are one of the three primary constituents of atoms. They form orbitals that surround the positively charged nucleus. In a free atom, the electrons' total negative charge balances the positive charge of the protons in the nucleus. Removal or addition of an atomic electron produces a charged ion. Free electrons (not bound to an atom) produce electrical conduction. Electronic devices, such as cathode-ray tubes, oscilloscopes and electron microscopes, use beams of electrons. An electron is a lepton (light particle). Its anti-particle is the positron (positive particle). See also Broglie, Prince Louis Victor de; chemical bond; matter; neutrons; particle physics; photoelectric effect; valence