Which of the following best describes a compound?

A compound is defined as a substance that consists of two or more different elements that are chemically bonded together in a fixed ratio. This means that the atoms within a compound are not merely mixed but are connected through chemical bonds, resulting in a substance with unique properties that differ from those of the individual elements.

For instance, water (H₂O) is a compound made of hydrogen and oxygen atoms that are chemically bonded. The chemical bonding imparts specific characteristics to water that cannot be found in pure hydrogen or oxygen alone.

This definition distinguishes compounds from mixtures, which involve the physical combination of substances without any chemical bonding. In the case of mixtures, the individual components retain their properties and can be separated through physical means. Thus, a compound must involve a chemical reaction that creates something new at the atomic level.