How many different isomers can be derived from ethylene if two hydrogen atoms are replaced by a fl uorine atom and a chlorine atom? draw their structures and name them. indicate which are structural isomers and which are geometric isomers?

             THREE different isomers can be derived from ethylene if two hydrogen atoms are replaced by a fl uorine atom and a chlorine atom.

Explanation:
                   When two Hydrogen atoms in ethylene (C₂H₄) are replaced with Fluorine and Chlorine atom then the new molecular formula is C₂H₂FCl.
                    Compounds having same Molecular formula but different structural formula are called as Isomers.
                     First Isomer of C₂H₂FCl is 1-chloro-1-fluoroethene, in which F and Cl at geminal position (attached to same Carbon atom).
                     Other two Isomers are Geometrical Isomers of 1-chloro-2-fluoroethene, in which F and Cl at different carbon atom and having different position is space. The one in which both F and Cl at opposite side forms (trans)-1-chloro-2-fluoroethene and the one in which both are in same side is called as (cis)-1-chloro-2-fluoroethene.