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Meaning of atom

at•om

Pronunciation: (at'um), [key]
— n.
  1. muonic atom; kaonic atom.
    1. the smallest component of an element having the chemical properties of the element, consisting of a nucleus containing combinations of neutrons and protons and one or more electrons bound to the nucleus by electrical attraction; the number of protons determines the identity of the element.
    2. an atom with one of the electrons replaced by some other particle:muonic atom; kaonic atom.
  2. this component as the source of nuclear energy.
  3. a hypothetical particle of matter so minute as to admit of no division.
  4. anything extremely small; a minute quantity.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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