Elements An element is one of 114 presently known substances that constitute matter. The atoms of one element have a certain number of protons and exactly the same number of electrons. They may howver have different masses (constituting different isotopes) if they have different numbers of neutrons. Elements (and chemical compounds) may occur in different structures called polymorphs.
Simple Molecules Under this category you will find simple inorganic molecules like salts, acids, bases, and also organic molecules such as common solvents, short chain hydrocarbons, cyclic hydrocarbons, and some heterocycles.