Chemical Bonding And Molecular Structure

More be the electronegatively difference, more be the polar character, thus correct order is

Except (iii) i.e. , all other show octahedral geometry.

has bonds and one lone pair of electrons, hence show distorted octahedral structure also known as pentagonal bipyramidal with one lone pair.

All other shows octahedral geometry.

(i) :

(Octahedral with no lone pair)

(ii) :

(Octahedral with no lone pair)

(iii) :

(Distorted octahedral with one lone pair)

(iv) :

(Octahedral with no lone pair)

The repulsion by the electrons in the same valence shell does not depend on the attraction of the bonding pair towards the nucleus. This is because electrons are identical in charge.

The repulsion can be minimised, if two electrons move as far apart as possible by occupying different degenerate orbitals or if they have parallel spins.

Covalent molecules are usually held in a crystal structure by van der Waals??attraction. (London forces, dipole-dipole interactions, dispersion).