WEB TUTORIAL - Group Theory
H2O Worked ExampleThe Number of Unchanged Bonds ( R)Number of symmetry elements, h = 4
C2v E C2 (z) v(xz) v(yz) Linear functions,
rotationsQuadratic
functionsCubic
functionsA1 +1 +1 +1 +1 z x2, y2, z2 z3, x2z, y2z A2 +1 +1 -1 -1 Rz xy xyz B1 +1 -1 +1 -1 x, Ry xz xz2, x3, xy2 B2 +1 -1 -1 +1 y, Rx yz yz2, y3, x2y You must consider the bonds which have moved, and hence how many bonds remain unchanged after the symmetry element has been completed. Not the atoms!
E.g. C2 rotation:
One atom has stayed in the same position, but imagine the bonds are labelled 'A' and 'B'. Thus following around the pictures, you can see that bond 'A' and bond 'B' have changed positions, hence for C2 rotation there are NO Unchanged bonds.Consider each symmetry element in turn, and answer how many unchanged bonds there are in each case after the symmetry element has been completed and pick one of the following answers.
The first number indicates the number of unchanged bonds for E, the second number
indicates the number of unchanged bonds for the C2 rotation and so forth.