Proper rotation axis Cn

This denotes an axis through the molecule about which a rotation of 360°/n can be carried out. For example, in H2O the C2 axis is a symmetry element (Fig. 6.1.1), which gives rise to the symmetry operation C2. (In this book all symmetry operations will be indicated in bold font.) Meanwhile, NH3 has a symmetry element C3 (Fig. 6.1.2), but now there are two symmetry operations 

Two views of SFg showing the C4 and C3 axes. In the figure on the right, the C3 axis is perpendicular to the paper and passes through the S atom. In both figures, a secondary C2 axis (the same one ) is also shown. 

Two views of cyclohexane showing the principal C3 axis (perpendicular to the paper in the figure on the right) and three secondary C2 axes. In the figure on the right, the + and — signs label the C atoms lying above and below the mean plane of the molecule, respectively. 

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Finally, we have five independent symmetry elements identity E, proper rotation axis Cn, symmetry plane ct, inversion center 7 and rotation- eflection axis generating... 

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