Isomersism

 Isomers are molecules with the same molecular formula but different structural formula. There are three types of isomerism, namely: Structural, functional and stereo isomerism. In structural isomerism the molecules have the same molecular formula but different structural formula, an example would be two molecules of the same molecular formula but with different lengths of their carbon back bone. Functional isomerism is where the molecules possess different functional groups but have the same molecular formula. And stereoisomers have the same molecular formula but different arrangements in space.