n-butane and iso-butane are chain isomers. Why? What is chain isomers and position isomers?

Chain isomers :

Compounds having same molecular formula but are  different in the arrangement of carbon atoms in straight or branched chains are referred to as chain isomers. n-butane and iso-butane differ in the arrangement of carbon atoms and  are therefore chain isomers.

 

             butane                                 iso-butane

 

 

Position isomers :

When two or more compounds with the same molecular formula differ in the position of substituent  atom or functional group on the carbon atom, they are called position isomers.

Example :