Smallest particle of a Compound that has all the chemical properties of that compound. Molecules are made up
of two or more Atoms, either of the same Element or of two or more different elements. Ionic compounds, such as common salt (see Sodium Chloride), are made up not of molecules but of ions arranged in a crystalline
structure (see Crystal). Unlike ions, molecules carry no electrical Charge. Molecules differ in size and Molecular Weight as well as in structure (see Isomer).