This video lecture from Fundamental Principles of Organic Chemistry (F.Sc. second year Chemistry) covers Stereo Isomerism. In this type of isomerism, 2 different molecules may have same molecular formula and even same structure but owing to different orientation in 3d space, they exist as different molecules or stereo isomers of each other. The first type of stereo isomerism is geometric isomerism also called cis-trans forms which originate because of the inability of a molecule to rotate freely about a double bond unlike alkanes which may rotate freely (giving rise to eclipsed and staggered configurations). 2 similar groups lying on the same side of double bond gives a cis- while similar groups lying across the double bonded carbon gives a trans- type isomer. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.