atomnoun [ C ]
uk/ˈæt.əm/us/ˈæt̬.əm/B2 the smallest unit of any chemical element, consisting of a positive nucleus surrounded by negative electrons. Atoms can combine to form a molecule:
A molecule of carbon dioxide (CO2) has one carbon atom and two oxygen atoms.
figurative He hasn't an atom of sense (= he has no sense), that boy.
More examples
- The nucleus of a deuterium atom contains a proton and a neutron.
- Scientists are working to harness the power of the atom.
Thesaurus: synonyms and related words
Physics: atoms, molecules & sub-atomic particles
- acceptor
- anion
- antilepton
- antimatter
- antineutrino
- antiparticle
- disaccharide
- elementary particle
- intramolecular
- ion
- ionize
- lepton
- Lewis structure
- macromolecule
- neutron
- quark
- relative molecular mass
- strong force
- subatomic particle
- subunit
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