Fig 1Point-group turntableDrag to turn · M mirror0° · E
point group C3v: E, 2C3, 3σv
Match lamp: lit when the molecule lands on itselfNH₃ on its C₃ axis rodTurn the table in steps of 360°/3. The molecule lands on itself at 120° (C₃) and 240° (C₃²); a full turn is E. Lower the mirror and the plane through the axis is a σv every 60°, because the three planes of NH₃ are 60° apart.