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Introduction Symmetry Operations Point Groups

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Symmetry Operations

Proper axes of rotation (Cn)


Rotation with respect to a line (axis of rotation) which molecules rotate. Cn is a rotation of (360/n)°. Each rotation brings you to the indistinguishable state for original.


Examples:


In this first example we do two improper rotations one after the other. Notice that 2 S4 = 1 C2.

H2O - A C2 axis There is a line(rotation of axis) passing through O. When you rotate H atoms 180° =(360/2)°, you get the same state.

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CH3Cl - C3 axis In this example, line passes thru C and Cl. And in order to get the same state, we need to rotate 120°.To see do a mouse over or play with the applet.

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BrF5 - C4 axis


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Real life example-Snowflakes C2, C3, C6 axes

Images from www.kacha-stones.com/crystal_healing.htm and www.scd.ucar.edu/news/00/fotoweek/1208.snowflake.html

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