Rotation-reflection, Improper axis (Sn)

This is a compound operation combining a rotation (C_n) with a reflection through a plane perpendicular to the C_n axis σ_h.(C_n followed by σ_h)

σC_n=S_n

Examples: In this first example we do two improper rotations one after the other. Notice that 2 S4 = 1 C2
2 S4 = 1 C2
Rotation Angle Symmetry Operation 90° S4 180° C2(=2S4)Above example 270° 3S4 360° E(=4S4) Try it and see !! S2 = i
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Can you see the S3? Click to see in details
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Mouse over to see S3 & S6
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3S4 axes. No C4 !! [Draw the molecule with C in the center and H's on appropriate vertices.] Like below:
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