What are molecules?
Molecules are the smallest unit of a matter that has individual existence and possesses all the properties of that matter. Molecules are made up of atoms that are held together by chemical forces, known as bonds. These bonds form as a result of the sharing or exchange of electrons among atoms. The atoms of certain elements readily bond with other atoms to form molecules. Examples of such elements are oxygen and chlorine. The atoms of some elements do not easily bond with other atoms. They form atomic molecules. Examples are neon and argon.
Molecules are formed by the union of one, two three, four or more atoms of the same element or different elements. Some molecules, notably certain proteins, contain hundreds or even thousands of atoms that join together in chains that can attain considerable lengths. These are called macromolecules. Thus, molecules can vary greatly in size, shape and complexity.