Consider a hypothetical planar molecule with the formula `A_(2)B_(2)X`(where `X` is the central atom). How may elements symmetry (plane of symmetry as well as centre of symmetry) does it have?

Options

A. `5`
B. `3`
C. `4`
D. `2`

Answer

C

Explanation

The centre of molecule `(X` atom) is a cnetre of symmetry `(C_(i))`. There are three planes of symmetry: They are `(1)` the plane through `A-X-A` and perpendicular to the plane of the paper, `(2)` the plane through `B-X-B` and perpendicular to the plane fo the paper and `(3)` the plane that cuts through all five atoms. This plane is the plane of the paper. All planar molecules are chiral beacuse the plane of the atoms is a plane of symmetry.
There is no restriction on the placement of a plane of symmetry as the plane can cut atoms in half or cut bonds between atoms. ON the other hand, there is a restriction on the placement of a cneter of symmetry in a molecule, either in empty space, in an atom, or in the center of a bond between atoms.