Here's why:

* Elements are pure substances that cannot be broken down into simpler substances. Examples include oxygen (O), nitrogen (N), and carbon (C).

* Compounds are formed when two or more elements chemically combine in a fixed ratio. Examples include water (H₂O) and carbon dioxide (CO₂).

* Mixtures are combinations of two or more substances that are not chemically bonded. The substances in a mixture retain their individual properties and can be separated by physical means.

Air is primarily composed of nitrogen (78%) and oxygen (21%), with small amounts of other gases like argon, carbon dioxide, and trace amounts of other gases. These gases are not chemically bonded, but rather are physically mixed together.

Therefore, air is a mixture, not a compound or an element.