Which best defines a compound?

A compound is best defined as two or more different types of atoms that are chemically bonded together. This definition highlights the fundamental characteristic of compounds: they consist of at least two different elements that combine in fixed ratios through chemical bonds, which can be ionic or covalent.

For instance, water (H2O) is a common compound made up of hydrogen and oxygen atoms. The chemical properties of a compound are often very different from those of the constituent elements, which is another key feature that differentiates compounds from simple mixtures or unbonded collections of atoms.

In contrast to the correct answer, a single element only contains one type of atom, while a mixture of elements consists of two or more elements that are not chemically bonded, retaining their individual properties. An unbonded collection of atoms does not form a compound, as it lacks the stable chemical bonds that characterize compounds.