Question

(vi) D3h point group has
(a) 3C3 axis and one C2 axis.
(b) C3axis and three C2 axis
(c) C3axis and one C2 axis.​

Answer 1

I think B is the right answer

Answer 2

D3h point group has C 3 axis and three C 2 axis

Explanation:

Option b is the answer - C 3 axis and three C 2 axis

Molecule are in D3h point group if it posses following symmetry elements-

• E ( identity )- all molecule posses this symmetry. The molecule remain as it is.

• One C 3 and three C 2 rotation - C 3 is a 120° rotation and C 2 is a 180° rotation.

• Reflection and symmetry plane (σ )- symmetry plane within the molecule leave the molecule indistinguishable. one σₙ reflection occur through horizontal plane which is perpendicular to principal axis and three σν reflection occur through vertical plane which is perpendicular to principal axis.

• Molecule which posses D3h point group are PCl₅ and BH₃