Butane and 2- methyl propane exhibit position isomerism.
The compound having the same molecular formula but the difference in the chain structure are called chain isomers. If the position of the functional group is different in the compound having the same molecular formula and the same functional group then they are called position isomers. Butane and 2- methyl propane has same molecular formula: C4H10.
Looking at the structure below of butane and 2- methyl propane we can say that they do not contain any functional group but their chain structure is different.
Therefore, butane and 2- methyl propane exhibit chain isomerism.