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DictionaryatomChemical unit
noun

atom

AT-uhm/ˈætəm/

The smallest particle retaining the identity of a chemical element.

The model shows a helium atom with a nucleus and electron cloud.

A single helium atom represented by a simple scientific model: a compact nucleus containing two protons and two neutrons, surrounded by a softly stippled electron cloud containing two schematic electron markers.
Etymology
aGreeknot
+tomGreekto cut

The pieces mean 'not cut,' expressing the ancient idea of an indivisible building block of the universe. That philosophical term was later revived scientifically for the chemical unit.

In context

The Organic Chemistry Tutor2:40
the only type of atom that we have in o2 are oxygen atoms
Elements, Atoms, Molecules, Ions, Ionic and Molecular Compounds, Cations vs Anions, Chemistry

More examples

  • An atom of carbon has six protons.
  • The molecules contain several different kinds of atoms.
  • Not an atom of evidence supported the rumor.

Forms

atom · atoms

atomic adjective — Relating to atoms or their structure.

Similar words

molecule
Contains bonded atoms and may include more than one element.
particle
Is broader and can describe objects smaller or larger than atoms.