HYBRIDISATION IN CHEMISTRY | TYPES AND THEIR EXPLANATIONS |

 in order to explain, the characteristics of geometrical shapes of polyatomic molecules like ch4, nh3, and h2o etc,. paulung introduced the concept of hybridisation. according to him, the atomic orbitals are known as hybrid orbitals. pure orbitals are not used to form bonds as like hybrid orbitals. the phenomenon is known as hybridisation which can be defined as the process of mixing of suitable atomic orbitals of an atom resulting in the formation of new set of orbitals of equivalent energies and shape. for the formation of sp3 hybrid orbitals, s and p orbitals are combined as 2s and three 2p orbitals.

salient features of hybridisation:

the main features of hybridisation are, 

1. in hybridisation, we do not mix the electrons. mix certain number of orbitals.
2. hybridised atomic orbitals are equal to the hybrid orbitals in number.
3. orbitals of same energy should be mixed to form hybrid orbitals.
4. the hybrid orbitals which are formed are equivalent in energy and shape.
5. hybrid orbitals are more effective in forming stronger bands that lead to the formation of more stable molecules
6. there is some gap between the orbitals, for having the minimum repulsions between the orbitals.

important conditions for hybridisation

• the orbitals present in the valance electronic shell of the atom are only hybridised. other orbitals are not involved.
• the orbitals must have comparable energy which undergoing for hybridisation.
• electron promotion is not an prior to the hybridisation as essential condition.
• only half filled orbitals should participate in hybridisation is no the the necessary thing. 
• in some cases, filed orbitals of valence shell take place in hybridisation.

TYPES OF HYBRIDISATION:

There is a lot of types of hybridisation. based on the orbitals s , p and d involving. the different types of hybridisation are:

SP HYBRIDISATION : 

• this type of hybridisation involves when there is a mixing of one s and one p orbital. this results in the formation of two equivalent sp hybrid orbitals. 
• s and Pz are the suitable orbitals for the sp hybridisation.
• if the hybrid orbitals are about to lie along z axis, then each sp hybrid orbitals has 50% s character and 50% p character. 
• such a molecule in which the central atom is sp hybridised and linked directly to two other central atoms possesses linear geometry.
•  this type of hybridisation is also known as diagonal hybridisation.
• example: becl2 is one of the example taken for sp hybridisation. 
• the electronic configuration of beriliem is 1S2 2S2 in ground state.
• In the excited state one of the 2s electrons is promoted to vacant 2p orbital to account for its bivalency.
• one 2s and one 2p orbital get hybridised to form two sp hybrid orbitals. 
• these two sp hybrid orbitals are oriented in opposite direction forming an angle of 180 degrees.
• all the hybridised sp orbitals overlaps with the 3p orbital of chlorine axially and form two be-cl sigma bonds. 

a) formation of sp hybrids from s and p orbitals;

b)formation of the linear becl2 molecule.

SP2 HYBRIDISATION

• there is an involvement of one s and two p orbitals in order to form three equivalent sp2 hybridised orbitals in this sp2 hybridisation. 
• example, BCl3 is taken as an example for the sp2 hybridisation.
• ekectron is promoted to vacant 2p orbital as a result boron has three unpaired electrons. 
• these three hybrid orbitals so formed are oriented in a trigonal planar arrangement and overlap with 3p orbitals of chlorine to form three bcl bonds.
• the geometry of bcl3 is trigonal planar with clbcl bond 
• the angle of the geometric structure is 120 degrees.

SP3 HYBRIDISATION

1. SP3D HYBRIDISATION
2. SP3D2 HYBRIDISATION