electron (e-)

One of the negatively charged particles that orbits the atomic nucleus within allowed energy shells. Electrons share properties of both waves & particles. Charge is 1e+. Mass is 1/1836.15 that of a proton. When emitted from a nuclear decay of a radioactive substance (beta-decay) electrons are beta-particles.

References

Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999