Which of the following is NOT a diatomic molecule?

• A. Oxygen gas (O2)
• B. Hydrogen gas (H2)
• C. Nitrogen gas (N2)
• D. Ozone (O3)

Answer: (D)

A diatomic molecule is made of exactly two atoms. Oxygen gas, hydrogen gas, and nitrogen gas each consist of two identical atoms bonded together, giving O2, H2, and N2. Ozone, however, has three oxygen atoms in one molecule (O3), so it is not diatomic. It’s a triatomic molecule, though still a form of oxygen with distinct properties from O2.