Molecule

Molecule - a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.


Molecules form when two or more atoms form chemical bonds with each other. It doesn't matter if the atoms are the same or are different from each other.

Molecules Versus Compounds Molecules made up of two or more elements are called compounds. Water, calcium oxide, and glucose are molecules that are compounds. All compounds are molecules; not all molecules are compounds.

What Is Not a Molecule?Single atoms of elements are not molecules. A single oxygen, O, is not a molecule. When oxygen bonds to itself (e.g., O2, O3) or to another element (e.g., carbon dioxide or CO2), molecules are formed.