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 ß particles. A nucleus and its electrons constitute an atom.
[electro- + -on]
See Also: shell
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Examples: glitazone, GI cocktail, etc.