Which term represents the basic unit of a chemical element?

The term that represents the basic unit of a chemical element is "atom." An atom is the smallest unit of matter that retains the properties of an element. Each atom consists of a nucleus made up of protons and neutrons, surrounded by orbiting electrons.

Atoms combine in various ways to form molecules, ions, and compounds. A molecule is formed when two or more atoms bond together, while an ion is charged because it has either lost or gained electrons. A compound, on the other hand, consists of two or more different types of atoms that are chemically bonded together. Therefore, while molecules, ions, and compounds are all important in chemistry, they are not the fundamental building blocks of chemical elements. The atom stands as the primary unit from which all matter is constructed, making it the correct answer for this question.