Here's a breakdown:

* Atom: The basic building block of matter. It's the smallest unit of an element that retains the chemical properties of that element.

* Molecule: Two or more atoms held together by chemical bonds. These bonds can be covalent (sharing electrons) or ionic (transferring electrons).

Examples of molecules:

* Water (H₂O): Two hydrogen atoms bonded to one oxygen atom.

* Carbon dioxide (CO₂): One carbon atom bonded to two oxygen atoms.

* Sugar (C₁₂H₂₂O₁₁): Many carbon, hydrogen, and oxygen atoms bonded together in a complex structure.

Important Notes:

* Not all groups of atoms are molecules. For example, a single atom of helium is not a molecule.

* Some molecules consist of only one type of atom. For example, oxygen gas (O₂) consists of two oxygen atoms.

Let me know if you have any more questions about atoms and molecules!