* Mixture: A combination of two or more substances where each substance retains its own chemical properties.

* Compound: A substance formed when two or more elements chemically combine in a fixed ratio.

* Element: A pure substance that cannot be broken down into simpler substances by chemical means.

Exhaled air primarily consists of:

* Nitrogen (N2): An element.

* Oxygen (O2): An element.

* Carbon Dioxide (CO2): A compound formed from carbon and oxygen.

* Water Vapor (H2O): A compound formed from hydrogen and oxygen.

Since exhaled air contains multiple substances that are not chemically bonded, it's classified as a mixture.