Dichloromethane, CH 2 Cl 2. There is a C 2 rotation axis which passes through the carbon atom and the midpoints between the two hydrogen atoms and the two chlorine atoms. Define the z axis as co-linear with the C 2 axis, the xz plane as containing CH 2 and the yz plane as containing CCl 2. A C 2 rotation operation permutes the two hydrogen atoms and the two chlorine atoms. Reflection in the yz plane permutes the hydrogen atoms while reflection in the xz plane permutes the chlorine atoms. The four symmetry operations E, C 2, σ(xz) and σ(yz) form the point group C 2 v. Note that if any two operations are carried out in succession the result is the same as if a single operation of the group had been performed.