You are here: Symmetry & Point Groups » Symmetry Operations » Reflection

Symmetry Operations

Planes and Reflection (σ)

Planes and Reflection
Molecules contain mirror planes.
  • σh(horizontal): plane perpendicular to principal axis
  • σd(dihedral), σv(vertical): plane olinear with principal axis
    • σd: σ parallel to Cn and bisecting two C2' axes
    • σv: Vertical, parallel to principal axis


Eye Glasses
eyeglasses with a reflection plane

Look at a pair of glasses and see the reflection symmetry from the center. There is no other symmetry.

hand with a reflection plane

Look at your hands to see reflection symmetry. Can you see any more symmetry operations?

chair with a reflection plane

Back to top


Mirror planes must either bisect the molecule or contain all atoms in a molecules. The mirror planes for H20are examples of each of these situations.

Back to top

Infinite planes
Is it hard to see infinite number of reflection planes? All of those planes contain all three atoms.

Back to top
2D structure image of benzene
How many planes can you see?

If you said 7 for the above question, you are on the right track. Guess which one is the seventh. For hint, check the water example above.

Back to top

Go to the previous page
molecule image for decoration
Go to the next page