Define the terms ‘compound’ and ‘molecule’

A 'compound' is a substance formed when two or more chemical elements are chemically bonded together. The atoms of the elements are held together by one of the several types of chemical bonds - covalent bonds, ionic bonds, metallic bonds, etc. The elements in any compound are always present in fixed ratios. Example of compounds include water (H2O), carbon dioxide (CO2), and sodium chloride (NaCl).

A 'molecule' is the smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atoms that are held together by chemical 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 molecules include the hydrogen molecule (H2), the nitrogen molecule (N2), and the water molecule (H2O).