Compounds are made of two or more different elements.
Let's look at some common gases:
* Oxygen (O₂) - This is an element, not a compound, as it's made up of only oxygen atoms.
* Nitrogen (N₂) - Another element, composed only of nitrogen atoms.
* Carbon dioxide (CO₂) - This is a compound because it's made of carbon (C) and oxygen (O) atoms.
* Water vapor (H₂O) - Also a compound because it's made of hydrogen (H) and oxygen (O) atoms.
* Methane (CH₄) - A compound containing carbon (C) and hydrogen (H) atoms.
* Helium (He) - An element, composed only of helium atoms.
Therefore, the following gases are compounds:
* Carbon dioxide (CO₂)
* Water vapor (H₂O)
* Methane (CH₄)
