Final answer:
Compounds consist of two or more elements chemically combined in a fixed proportion, as exemplified by water (H₂O), which is made of hydrogen and oxygen in a 2:1 ratio.
Step-by-step explanation:
Compounds are pure substances that by definition consist of two or more elements in combination.
A compound is a substance that contains two or more elements chemically combined in a fixed proportion. For instance, carbon and hydrogen combine to form various compounds such as methane, which always has a fixed ratio of one carbon atom to four hydrogen atoms. A molecule of water (H₂O) is another classic example of a compound consisting of two hydrogen atoms chemically bonded to one oxygen atom.
In essence, compounds are homogeneous; they have a uniform composition throughout and cannot be separated into their constituent elements by physical methods, only by chemical means. The chemical formula of a compound, such as H₂O for water, provides information on the elements present and their constant ratio in the molecule.