In Structural isomerism, the atoms are arranged completely in a different manner. Chain isomerism where the isomers differ in the order in which the carbon atoms are bonded to each other. Position isomerism where the main carbon skeleton is same, but they differ in the position of functional group attached to it. Functional group isomerism where isomers differ in functional group. In one of them, butane, the carbon atoms lie in a "straight chain".
