Here's why:

* Elements are the simplest pure substances. They consist of only one type of atom. Examples: gold (Au), oxygen (O), carbon (C).

* Compounds are formed when two or more different elements chemically combine in a fixed ratio. Examples: water (H₂O), carbon dioxide (CO₂), table salt (NaCl).

Let's break it down:

* Water (H₂O) is a compound because it contains two hydrogen atoms (H) and one oxygen atom (O).

* Carbon dioxide (CO₂) is a compound because it contains one carbon atom (C) and two oxygen atoms (O).

* Table salt (NaCl) is a compound because it contains one sodium atom (Na) and one chlorine atom (Cl).

Important note: Mixtures, like saltwater, contain different elements but are not chemically combined, so they don't fit the definition of a compound.