homologous series

An homologous series is a series of related organic compounds that share similar properties and the same general formula, differing only by a single, unchanging collection of atoms. A notable example is the alkane hydrocarbon group, the general formula of which is C2H2n+2. Therefore each member of the group changes by a CH2 group – methane (CH4), ethane (C2H6), propane (C3H8), etc. Successive members of a homologous series are called homologues.