Hybridization was introduced by Pauling, to explain the equivalent nature of covalent bonds in a molecule. It can also be defined as the mixing of different shapes and approximate equal energy atomic orbitals and redistribution of energy to form a new orbital, of the same shape and the same energy. These new orbitals are called hybrid orbitals and the phenomenon is called Hybridization. Consider an example of Be compound. If it is formed without Hybridization then both the Be---Cl bond should have different parameters and p---p bond strength > s---p bond strength. Practically bond strength and distance of both the Be---Cl bonds are the same. This problem can be overcome if the Hybridization of s and p orbital occurs. Now after considering s---p Hybridization in Beryllium Dichloride, Cl----Be-----Cl. Here in the first bond from the left side p---sp Hybridization is present and in the second bond sp---p Hybridization, so here bond strength of both bonds will be equal.
Characteristic of Hybridization
Hybridization is a process of mixing orbitals and not electrons. Therefore in Hybridization full-filled, half-filled, and empty orbitals may take part. A number of the hybrid orbitals formed is always equivalent to the number of atomic orbitals which may take part in the process of Hybridization. Each hybrid orbital has two lobes, one is longer, and the other is smaller. The bond will be formed from a large lobe. The number of hybrid orbitals on the central atom of a molecule or ion = number of sigma bonds + lone pair of electrons. The 1st bond between two atoms will be sigma. The other bond between the same two atoms will be a pi bond. Maximum two pi bonds may be present on a single atom. The electron pair of an atom which does not take part in bond formation is called a lone pair of electrons. One element can represent many Hybridization states depending on experimental conditions, for example, C showing sp,sp2, sp3 Hybridization in its compounds.
The repulsion between lp--lp > lp---bp > bp---bp. Hybrid orbitals are differentiated as sp, sp2, sp3, etc. The directional properties in a hybrid orbital are more than atomic orbitals. Therefore hybrid orbitals form stronger sigma bonds. The directional property of different hybrid orbitals will be in the following order. sp < sp2 < sp3 < sp3d2 < sp3d3. In dsp3 and d2sp3 Hybridization, different quantum numbers are being used.
Determination of Hybridization State
Method 1: Count the following pair of an electron around the central atom:
Method 2: Th predict Hybridization following formulae may be used:
Number of hybrid orbitals = ½ ( total number of the valence electron in the central atom + total number of the monovalent atom - charge on cation + charge on anion )
Hybridization of Ethene ( C2H4 )
C2H4 has an sp2 Hybridization process. In this Hybridization one ‘s’ and two ‘p’ orbitals are mixed to give three new sp2 hybrid orbitals which all are in the same shape and equivalent energies. These three sp2 hybrid orbitals are at an angle of 120 degrees and give a trigonal planar shape. Ethene has two 2CH molecules and 4H molecules. Carbon consists of 6 electrons and hydrogen has 1 electron. During the formation of CH2=CH2, the electronic configuration of carbon in its ground state (1s2 2s2 2p1 2p1) will change to an excited state and change to 1s2 2s1 2px12py1 2pz1. In an excited state, carbon needs an electron to form bonds; one of the electrons from the 2s2 orbital will move to 2pz orbital to give four unpaired electrons.
Geometrical Structure of Ethene
Ethene is not a very complex molecule. The carbon atoms of ethene are doubly bonded to each other apart from this carbon atom is also bonded with two Hydrogen atoms. They combine to form a total of three bonds to each carbon atom, giving them an sp2 Hybridization. As a carbon atom is forming three sigma bonds instead of four sigma bonds, so they also need to hybridize three of its outer orbitals, instead of four orbitals. A carbon atom is forming three sigma bonds instead of four orbitals. These three orbitals are formed by 2s electrons and 2p electrons, forming bonds in ethene.
One Word Answer
1. Write the structural formula for Ethene?
2. Which type of Hybridization is present in Ethene?
Ans: sp2 hybridization
3. What is the angle present in sp2 Hybridization?
Ans: 120o degree
Five Basic Shapes of Hybridization
The five basic shapes of hybridization are