Q10.93 CP - Chemistry: Molecular Nature Of Matter And Change

Question

A molecule of formula AY3 is found experimentally to be polar. Which molecular shapes are possible and which are impossible for AY3?

Step-by-Step Solution

Answer

The molecule is polar the possible structures include Pyramidal and T-shaped

Step 1: Definition

A polar molecule is a molecule that has a charge on one side of the molecule, that is not cancelled out.

Step 2: Possible structures

Due to the asymmetry of the triangular pyramidal structure, the bond dipoles do not cancel out, making the molecule generally polar.

For example Ammonia $\left({\mathbf{NH}}_{\mathbf{3}}\right)$ has a trigonal pyramidal structure and it is a polar molecule.

The molecule has a trigonal pyramidal structure. Due to the need that the two lone pairs on this electronic geometry be at equatorial positions, the molecular geometry must be T-shaped. The five trigonal pyramidal sections' completely cancel symmetry is broken by the lone pair of electrons, which makes the entire molecule polar.

For example: ${\mathbf{ClF}}_{\mathbf{3}}$  has a T-shaped structure and is a polar molecule.

Step 2: Impossible structures

a) Planar structure 

        A symmetric planar structure is non-polar because its dipole moments cancelled out

b)Tetrahedral structure

        A symmetric tetrahedral molecule will be non-polar because its dipole moments cancelled out.