Final answer:
Compounds and elements are classified as chemical substances; an element consists of only one type of atom, while a compound is made up of two or more chemically bonded elements in a fixed ratio.
Step-by-step explanation:
Compounds and elements are both classified as chemical substances. An element is a substance that cannot be broken down into simpler substances by chemical means and consists of atoms of only one kind. On the other hand, a compound is a substance formed when two or more elements are chemically bonded together in a fixed ratio, and it has properties different from its constituent elements. For instance, water (H2O) is a compound composed of hydrogen and oxygen in a 2:1 ratio.
To help classify some common substances, we consider salt (sodium chloride) as a compound, pure water (H2O) as a compound, soil as a heterogeneous mixture, salt water as a homogeneous mixture, pure air as a homogeneous mixture, carbon dioxide (CO2) as a compound, gold (Au) as an element, and bronze as a heterogeneous mixture because it is an alloy.