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atom

Syllabification: (at·om)
Pronunciation: /ˈatəm/

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Definition of atom

noun

  • the basic unit of a chemical element.
  • atoms as a source of nuclear energy:the power of the atom
  • [usually with negative] an extremely small amount of a thing or quality:I shall not have one atom of strength left

An atom, roughly 108 cm in diameter, consists of a tiny, dense, positively charged nucleus made of neutrons and protons, surrounded by a cloud of negatively charged electrons. Each chemical element consists of atoms that possess a characteristic number of protons. Atoms are held together in molecules by sharing electrons

Origin:

late 15th century: from Old French atome, via Latin from Greek atomos 'indivisible', based on a- 'not' + temnein 'to cut'

atom in other Oxford dictionaries

Definition of atom in the British & World English dictionary