Isomers which have their atoms connected in the same sequence but differ in the way the atoms are oriented in space - i.e. the difference between two stereoisomers lies only in the three dimensional arrangement of atoms. since Cis-3-hexene to trans-3-hexene differs in three dimensional arrangement of atoms and arrangement is same in 2D space , they are stereo isomers Solution Isomers which have their atoms connected in the same sequence but differ in the way the atoms are oriented in space - i.e. the difference between two stereoisomers lies only in the three dimensional arrangement of atoms. since Cis-3-hexene to trans-3-hexene differs in three dimensional arrangement of atoms and arrangement is same in 2D space , they are stereo isomers.