* Water (H₂O): Water is a completely different molecule, composed of hydrogen and oxygen.

* Oxygen (O₂): This is the gas we breathe, and it's a different molecule than carbon dioxide.

* Nitrogen (N₂): The most abundant gas in the atmosphere, nitrogen is a different molecule than carbon dioxide.

* Methane (CH₄): This is a greenhouse gas, but it has a different chemical composition than carbon dioxide.

* Sodium chloride (NaCl): This is table salt and is an ionic compound, not a molecule like carbon dioxide.

* Sugar (C₁₂H₂₂O₁₁): Sugar is a complex carbohydrate, with a much larger and different structure than carbon dioxide.

Key takeaway: A nonexample of carbon dioxide is any substance that is not made up of one carbon atom and two oxygen atoms bonded together (CO₂).