Answer:
W and Z
Explanation:
Atoms of the SAME element OR two atoms of DIFFERENT elements will form a MOLECULE.
E.g. 2 atoms of hydrogen + 1 atom of oxygen => 1 molecule of water. This 1 molecule of water can also be called a compound.
Also, 2 atoms of Oxygen can combine to form 1 molecule of Oxygen. This 1 molecule of Oxygen cannot be referred to as a compound.
Atoms of DIFFERENT elements form a COMPOUND.
Therefore, compounds are molecules, but molecules are not compounds.
Thus, the combination of atoms that will form a molecule, but not a compound is:
W(oxygen) + Z(oxygen) = molecule