* Element: A pure substance made up of only one type of atom (like oxygen or nitrogen).

* Compound: A substance formed when two or more different elements are chemically bonded together (like water, which is made of hydrogen and oxygen).

* Mixture: A combination of two or more substances that are not chemically bonded. Each substance retains its own properties.

Air is primarily composed of nitrogen and oxygen, but it also contains small amounts of other gases like argon, carbon dioxide, and water vapor. These gases are not chemically bonded, and their proportions can vary depending on location and weather conditions.