noun

"Atom" in English refers to the basic unit of a chemical element. It's the smallest particle of an element that retains its chemical properties. Atoms are composed of a nucleus (containing protons and neutrons) surrounded by electrons.

Example

1. An atom is the smallest particle of an element that still has the same chemical properties.
2. The atom is the building block of all matter.
3. Atoms are composed of protons, neutrons, and electrons.