The electron is a subatomic particle carrying an electric charge of
Coulombs – called the fundamental or unit charge, since all free charges are multiples of this charge - and a mass of
about 1/1836 the mass of a proton. The electron has spin equal to
which means it is a fermion.
The antiparticle of the electron is called the positron, which is identical to the electron except that it carries negative positive electric charge. When an electron collides with a positron, they may either scatter off each other or be totally annihilated, producing a pair (or more) of gamma ray photons. Electrons, which belong to the first generation of the lepton particle family, participate in gravitational, electromagnetic and weak interactions. Like all matter, they have quantum mechanical properties of both particle and wave, so they can collide with other particles and be diffracted like light. Since an electron is a fermion, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle.
In many physical phenomena, such as electricity, magnetism, and thermal conductivity, electrons play an essential role. An electron in motion relative to an observer generates a magnetic field, and will be deflected by external magnetic fields. When an electron is accelerated, it can absorb or radiate energy in the form of photons. Electrons, together with atomic nuclei made of protons and neutrons, make up atoms. However, electrons contribute less than 0.06% to an atom's total mass. The attractive Coulomb force between an electron and a proton causes electrons to be bound into atoms, forming a 'little solar system'. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding.
According to theory, most electrons in the universe were created in the big bang, but they may also be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere. Electrons may be destroyed through annihilation with positrons, and may be absorbed during nucleosynthesis in stars. Laboratory instruments are capable of containing and observing individual electrons as well as electron plasma, whereas dedicated telescopes can detect electron plasma in outer space. Electrons have many applications, including welding, cathode ray tubes, electron microscopes, radiation therapy, lasers and particle accelerators.