Final answer:
Carbon monoxide consists of two atoms with a triple bond, thus not forming a diatomic molecule, while water is a tri-atomic molecule composed of one oxygen and two hydrogen atoms.
Step-by-step explanation:
The compounds carbon monoxide (CO) and water (H₂O) consist of tri-atomic and diatomic molecules, respectively. Carbon monoxide has a triple bond between the carbon and oxygen atoms, forming a molecule with two atoms. Thus, it is not a diatomic molecule but rather a molecule of two different atoms with multiple bonds.
Water, on the other hand, is a compound composed of two hydrogen atoms and one oxygen atom, making it a tri-atomic molecule. Each water molecule is formed by single covalent bonds between the oxygen and the hydrogen atoms.