Key for Assignment of Point Groups

by
 1 Is the molecule linear? Yes- Go to 2
No- Go to 3
 2 Does it have a centre of inversion? Yes- Belongs to D∞h
No- Belongs to C∞v
 3 Does it have three or more different Cn axes with n > 2? Yes- Go to 4
No- Go to 5
 4 Does it have a C5 axis? Yes- Belongs to I or Ih
No- Belongs to T, Td, Th, O or Oh.
 5 Does it have a rotational axis Cn with n > 1? Yes- Go to 8
No- Go to 6
 6 Does it have a mirror plane? Yes- Belongs to Cs.
No- Go to 7
 7 Does it have a centre of inversion? Yes- Belongs to Ci.
No- Belongs to C1.
 8 Are there n C2 axes perpendicular to the principle axis, Cn? Yes- Go to 9
No- Go to 11
 9 Is there a horizontal mirror plane? Yes- Belongs to Dnh.
No- Go to 10
10 Are there n dihedral mirror planes? Yes- Belongs to Dnd.
No- Belongs to Dn.
11 Is there a horizontal mirror plane? Yes- Belongs to Cnh.
No- Go to 12
12 Are there n vertical mirror planes? Yes- Belongs to Cnv.
No- Go to 13
13 Are there any S2n axes? Yes- Belongs to S2n.
No- Belongs to Cn.