48 valence electrons

Molecular geometry is AX6 which is octahedral.

sp3d2

Octahedral

Main postulates are i) The exact shape of molecule depends upon no of electron pairs (bonder or non – bonded) around the central atom. ii) The electron pairs tend to repel each other since they exist around the central atom and the e- clouds are negatively charged.

(a) The shape of the molecule depends upon the number of electron pairs present in the valence shell around the central atom in a molecule. (b) Pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged.

Limitations of Valence Bond Theory They are: It fails to explain the tetravalency of carbon. This theory does not discuss the electrons’ energies. The assumptions are about the electrons being localized to specific locations.

In VBT, atomic orbitals which form molecular orbitals, do not retain their individual characteristic nature. In VBT, bonds are localized to two atoms and not molecules. In MOT, bonds are localized to both two atoms and molecules. VBT has simplicity and convenience especially in terms of calculations.

1. In vbt atomic bonds which develop are monocentric and mot develops molecular bond of polycentric. 2. Vbt can take form to produce the presence of ionic character whereas Mot is not capable of producing or predecting such effect.

Valence bond (VB) theory assumes that all bonds are localized bonds formed between two atoms by the donation of an electron from each atom. The theory assumes that electrons occupy atomic orbitals of individual atoms within a molecule, and that the electrons of one atom are attracted to the nucleus of another atom.