Question

define atoms. particles that make up matter, too small to see but detectable by other means. a form of energy that can be converted into matter. a type of molecule that can exist independently. the smallest unit of a chemical element that retains its properties.

Explanation:

An atom is the smallest unit of a chemical element that retains its properties. Atoms are the building - blocks of matter. The first option is too general about particles making up matter. The second option is about energy conversion, not atoms. The third option is about molecules, not atoms.

Answer:

The smallest unit of a chemical element that retains its properties.