- One of the negatively charged subatomic particles that orbit the positive nucleus, in one of several energy levels called shells; in mass they are estimated to be 1/1836.15 of a proton; when emitted from inside the nucleus of a radioactive substance, electrons are called β particles. A nucleus and its electrons constitute an atom. SEE ALSO: shell. [electro- + -on]- Auger e. an e. ejected from an orbital by photoelectric interaction with a photon emitted when another e., in a higher energy orbital, passed from a higher to a lower energy level; the Auger e. recoils with energy equal to the characteristic radiation less the difference in shell binding energies. See photoelectric effect, transition e..- internal conversion e. an e., similar to an Auger e., released from one of the e. orbits of the atom upon activation by a gamma ray from that atom's nucleus; the e. has kinetic energy equal to the net energy transition of the disintegration.- transition e. an e. that moves from one energy level to another to fill a vacancy in a shell, with the emission of characteristic radiation.
* * *elec·tron i-'lek-.trän n an elementary particle consisting of a charge of negative electricity equal to about 1.602 × 10-19 coulomb and having a mass when at rest of about 9.109534 × 10-28 gram or about 1/1836 that of a proton
* * *elec·tron (e-lekґtron) [Gr. ēlektron amber, because an electric charge can be produced in amber by rubbing] an elementary particle possessing the unit quantum of (negative) electric charge, 1.6 Ð§ 10−19 coulomb, with mass 1/1836 that of a proton, or 9.11 Ð§ 10−31 kilogram. Electrons can exist as atomic constituents or in the free state; flowing in a conductor they constitute an electric current; when ejected from a radioactive substance, they constitute beta rays; and when revolving about the nucleus of an atom they determine all of its physical and chemical properties except mass and radioactivity. Symbol e or e−. See also atom.
Medical dictionary. 2011.