 A chemical group or chemical species exhibits a distinctive reaction behavior or a distinctive spectral signal when analyzed by various spectroscopic methods.These three groupings are often used to describe the groups of elements that exist within an organic molecule.The following list of neutral compounds, anions, cations, functional groups and chemical species is a partial list of the many groups of elements that can exhibit or have a unique "chemical state" while being part of the surface or the bulk of a solid state material.