The word isomer is from the Greek and means having equal parts. Isomers in chemistry
are compounds that have the same number and type of atoms but which are interconnected
differently and thus have different physical properties. Figure 2-9a shows two
hydrocarbon isomers, n-butane and isobutane. Note that each has the same number of
carbon and hydrogen atoms (C4HlO), but they are differently interconnected and have
different properties.