There are three types of isomerism:1) Structural isomerism - Occurs when compounds which have the same molecular formula (eg. C4H9Br1) but have different atomic arrangements. Eg. CH2Br-CH2-CH2-CH3CH3-CHBr-CH2-CH32) Geometric Isomerism - Occurs when there are two different groups on either side of a C=C double bond , which has restricted rotation. There are two types of Isomers, Cis & Trans = Z & E HBrC=CHCH33) Stereoisomerism - Compounds with the same molecular formula but groups around a chiral carbon are arranged differently and non-superimposable (Like hands).