Then the … groups (n=even) are obtained. Naturally n must be even since … when n is odd and both…and…exist independently. These groups (n = odd) are conventionally designated … . Also,when n=2, the S2 group (remember S2=i) is conventionally called … If we add to a … group … (n odd) or … and… (n even) mirror planes,but no other rotation axes, then the … group are generated. If to the elements of … we add a horizontal mirror plane, then we generate the … groups. The product of … and … also generate an … symmetry element and its associated operations.งเคมี