Final answer:
Chemical compounds contain elements that are chemically combined in fixed proportions. Molecules of compounds have two or more different types of atoms, differentiating them from molecules of single elements.
Step-by-step explanation:
Every chemical compound contains elements. These elements are chemically bonded together in fixed proportions to form a compound. Unlike molecules of elements, which contain only one type of atom, molecules of compounds contain two or more different types of atoms. For instance, a molecule of water (H₂O) always consists of two hydrogen atoms and one oxygen atom, making it a compound comprised of hydrogen and oxygen elements. Similarly, glucose, a compound, and important body fuel, is always composed of carbon, hydrogen, and oxygen in a 6:12:6 ratio. Each compound has unique properties that differ from the properties of the individual elements that compose it. Compounds can be broken down into simpler substances, which are the elements that make them up, whereas elements themselves cannot be broken down by chemical means into simpler substances.