Question

What are the postulates of valence bond theory ?

Answer 1

Valence bond theory :
i) The Central metal. atom/ion Makes available a number of vacant orbitals equal to its coordination number
ii) These vacant orbitals form covalent bonds with the ligand oerbitals.
iii) A covalent boil& is formed by the overlap of vacant metal orbital and filled ligand orbitals. This complete overlap leads to the formation of a metal ligand, a bond.
iv) A strong covalent is formed only when the . orbitals overlap to the Maximum extent. This maximum overlapping is possible only when the metal vacant orbitals undergo process called.
A hybridised orbital characteristics than an has a better directional unhybtidised one.
v) The following table gives the coordination number, orbital hybridisation and spatial geometry of the more important geometries.

Coordination number	Types of hybridisation	Geometry
2	$s{p}^1$	linear
4	$s{p}^3$	tetrahedral
4	$s{p}^2$	square planar
6	$d^{2}s{p}^3$	Octahedral
6	$s{p}^3{d}^2$	Octahedral

Magnetic moment
A species having atleast one unpaired electron, is said to be pan magnetic. It is attracted by an external field. The paramagnetic moment is given by, the following spin-only formula
${\mu }_3=\sqrt{n(n+2)BM}$
${\mu }_3$= spin-only magnetic moment
n = number of unpaired electrons
BM = Bohr magneton, the unit which expresses the magnetic moment.