Final answer:
An element is a pure substance made up of one type of atom, a compound is a pure substance consisting of two or more elements chemically combined, and a mixture is a combination of substances that are not chemically combined. Air is a mixture of various gases and particles.
Step-by-step explanation:
Element: An element is a pure substance that consists of only one type of atom. It cannot be broken down into simpler substances by chemical means. Examples of elements include oxygen (O), carbon (C), and gold (Au).
Compound: A compound is a pure substance that consists of two or more elements chemically combined in a fixed ratio. They can be broken down into simpler substances through chemical reactions. Examples of compounds include water (H2O) and carbon dioxide (CO2).
Mixture: A mixture is a combination of two or more substances that are not chemically combined. The composition of a mixture can vary and can be separated through physical means. Examples of mixtures include air, salt water, and soil.
Air: Air is a mixture of gases, primarily nitrogen (78%), oxygen (21%), and small amounts of other gases such as carbon dioxide, argon, and trace gases. It also contains water vapor and various particles. Therefore, air is considered a mixture.