What is the best description of a molecule

To define molecules is a group of at least two atoms of a certain location that are linked to chemical bonds.

Explanation:

molecule of an element is composed of at least two types of atoms.

several atoms of a single chemical element, as in the case of oxygen. (O2) Atoms of different elements, as in the case of water. (H2O)

Molecule is a tiny or small piece of something.

Explanation: An extremely small particle or substance, especially at cellular or structure level.