THEORIES OF COVALENT BONDING (VB Theory) Cont....

The remaining types of hybridization are discussed in this post with clear pictures and animated videos. Hope this will make you understand better.

sp³d hybridization :

The mixing of one s ,three p and one d-atomic orbitals to form five sp³d hybrid orbitals of equal energy is called sp³d hybridization

Example:  PCl₅

The ground state electronic configuration of phosphorus atom is: 1s² 2s²2p⁶ 3s²3p_x¹3p_y¹3p_z¹.

 Phosphorus atom undergoes excitation to promote one electron from 3s orbital to one of empty 3d orbital.

Thus the electronic configuration of 'P' in the excited state is 1s² 2s²2p⁶ 3s¹3p_x¹3p_y¹3p_z¹ 3d¹.

Intermixing of half - filled one 3s, three 3p and one 3dz orbitals to give five  sp³d hybrid orbitals. The shape of the the orbitals participating in sp³d hybridization are shown below.

The sp³d hybrid orbitals which are arranged in trigonal bipyramidal symmetry are shown in the diagram below.

IMPORTANT:

 The five orbitals in sp³d hybridizationare not equivalent. These are divided into two sets :

a) Equatorial hybrid orbitals :

       Three hybrid orbitals are directed towards the corners of an equilateral triangle are called equatorial  hybrid orbitals. These are planar and bond angle is 120⁰.

b) Axial hybrid orbitals :

Two hybrid orbitals are perpendicular to the plane of equatorial hybrid orbital .These are called axial hybrid orbital . They make an angle of 90⁰ with equatorial hybrid orbitals.

Diagram showing equatorial and axial bonds in PCl5.

Geometry :  trigonal bipyramidal. 

Bond angle is 90⁰ and 120⁰.

sp³d² hybridization :

          The mixing of one s, three p and  two d- atomic orbitals to form six equivalent sp³d² hybrid orbitals of equal energy. This hybridization is known as sp³d² hybridization.

The electronic configuration of 'S' in ground state is 1s² 2s²2p⁶ 3s²3p_x²3p_y¹3p_z¹.

  Promotion of two electrons (one from 3s and one from 3p_x)into two of the 3d orbitals gives the excited state configuration of 1s² 2s²2p⁶ 3s¹3p_x¹3p_y¹3p_z¹3d².

In the  excited state, sulfur under goes sp³d² hybridization by mixing a 3s, three 3p and two 3d orbitals. Thus formed six half filled sp³d² hybrid orbitals are arranged in octahedral symmetry. 

Diagram showing the shape of orbitals involved in sp³d² hybridization

In SF6, four out of six hybrid orbitals are lying in one plane while remaining two are directed above and below the plane containing four hybrid orbitals  perpendicularly.

Geometry:  octahedral 

 Bond angle:  90⁰.

Sp³d³ hybridization :

        The mixing of one s, three p and  three d- atomic orbitals to form seven equivalent sp³d³hybrid orbitals of equal energy. This hybridization is known as sp³d³ hybridization.

Example :  IF₇

The electronic configuration of Iodine atom in the ground state is: [Kr]4d¹⁰5s²5p⁵. Since the formation of IF₇ , the iodine atom promotes three of its electrons (one from 5s orbital and two from 5p sublevel) into empty 5d orbitals. 

The electronic configuration of Iodine in the  excited state can be written as: [Kr]4d¹⁰5s¹5p³5d³.

 

In the excited state, iodine atom undergoes sp³d³ hybridization to give 7 half filled sp³d³ hybrid orbitals in pentagonal bipyramidal symmetry. These will form 7 σ_sp3_d3_-p bonds with fluorine atom. Diagram below shows the orbitals involved in the formation of IF7.

Geometry:  pentagonal bipyramidal  

Bond angle:  72⁰ and 90⁰.

Courtesy:

https://chemistryonline.guru/hybridization.

https://www.adichemistry.com/general/chemicalbond/vbt/hybridization-illustrations.html