Class 11 Chemistry Chapter 4 Chemical bonding and molecular structure
Concept of hybridization was first introduced by Pauling. He explained shapes of polyatomic molecules. He found that, atomic orbital combine to form new set of equivalent orbitals known as hybrid orbitals. However, these hybrid orbitals are used for forming bond. This phenomena was called as hybridization. Therefore, hybridization is phenomena of intermixing of atomic orbitals having similar energies, to form new set of orbitals with equivalent energies and identical shape.
Features of hybridization
- Number of hybrid orbitals is same as number of atomic orbital that get hybridized
- Hybridized orbitals have equal energy and shape
- Shape of hybrid orbitals is different than pure atomic orbitals undergoing hybridization
- In hybrid orbitals, electron density is concentrated at one side
- Hybrid orbitals are oriented in space to minimize repulsion between electrons and gain maximum symmetry
Conditions for Hybridization
- Hybridization takes place only with the orbitals of valence shell
- However, hybridization takes place between orbitals of similar energy
- Moreover, for hybridisation to occur promotion of electron form lower energy level to higher energy level is not necessary.
- Not only half filled but also filled orbitals can take part in hybridization (in some cases)
Lets now speak about different types of hybridization
sp hybridization:
sp hybridization
It is also known as linear or diagonal hybridization. In sp hybridization, intermixing of one s orbital and one p orbital leads to formation of two equivalent sp hybridised orbitals. New formed hybrid orbitals lie along the same line in opposite direction with linear geometry. Each hybrid orbitals have 50% s character and 50 % p character. Formation of BeCl2 molecule takes place due to sp hybridization
sp2 hybridisation:
sp2 hybridization
The intermixing of one s orbital and two p orbitals leads in formation of three sp2 hybridized orbitals. These hybrid orbitals get aligned, in trigonal planar symmetry with 120° angle between them. Each hybrid orbitals have 33% s character 66.6% of p character. Formation of BCl3 undergoes sp2 hybridisation.
sp3 hybridisation:
sp3 hybridization
The intermixing of one s orbital and three p orbitals of valence shell leads to formation of four, sp3 hybridized orbitals with equivalent energies and shape. These four hybrid orbitals forms tetrahedral geometry with 109.5° angle between them. Each hybrid orbitals have 25%, s character and 75% p character. Formation of CH4 undergoes sp3 hybridization.
Keywords: Hybrid orbitals, s orbital, p orbital, s character, p character
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