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 approximately equal energy atomic orbitals, and redistribution of energy to form new orbitals, of the same shape and same energy. These new orbitals are called hybrid orbitals and the phenomenon is called hybridization.
Consider an example of a compound, BeCl2. If it is formed without hybridization then both the Be---Cl bond should have different parameters as the p---p bond strength is greater than the 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 orbitals occurs. Now after considering sp 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 is present. So, the bond strengths of both bonds will be equal.
Characteristics of Hybridization
1. Hybridization is a mixing of orbitals and not electrons. Therefore in hybridization full filled, half-filled and empty orbitals may participate.
2. The number of hybrid orbitals formed is always equivalent to the number of atomic orbitals that may take part in the process of hybridization.
3. Each hybrid orbital has two lobes, one is longer, and the other is smaller. The bond will be formed from a larger lobe.
4. The number of hybrid orbitals on the central atom of a molecule or ion = number of sigma bond + lone pair of electrons.
A. The 1st bond between two atoms will be sigma.
B. The other bond between the same two atoms will be the pi bond.
C. At the maximum, two pi bonds may be present on a single atom.
D. The electron pair of an atom which does not take part in bond formation is called a lone pair of electrons.
5. One element can represent many hybridization states depending on experimental conditions, for example, a C atom shows sp,sp2, sp3 hybridization in its compounds.
The repulsion between lp--lp > lp---bp > bp---bp.
6. Hybrid orbitals are differentiated as sp, sp2, sp3, etc.
7. The directional properties in a hybrid orbital are more than the 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
8. In dsp3 and d2sp3 hybridization, different quantum numbers are being used.
Determination of Hybridization State
Method 1: Count the following pair of electrons around the central atom.
a. Count all pure sigma bonded electron pairs.
b. Count all lone pairs of electrons.
c. Count coordinate bonds.
d. Count negative charges.
Method 2: The following hybridization formulae may be used.
Number of hybrid orbitals = ½ (total number of valence electrons in the central atom + total number of monovalent atoms - charge on cations + charge on anions)
Hybridization of SF6
Number of hybrid orbitals in SF6 = ½ (6+6) = 12/2 = 6
Therefore SF6 has sp3d2 hybridization. In this hybridization, 1 s-orbital, 3 p-orbital, and 2 d-orbitals are mixed to give 6 new hybrid orbitals known as sp3d2 hybrid orbitals. The shape of molecules obtained from the above 6 hybrid orbitals will be symmetrical, octahedral, and the angle between all hybrid orbitals will be 90 degrees. Example: SF6. Two ‘d’ orbitals participating in the hybridization are dx2---y2, and dz2.
SF6 Hybridisation Diagrammatic Representation
The Geometry of SF6
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Sulphur hexafluoride is a type of greenhouse gas. It is also an inorganic and non-polar gas. It can be prepared by combining S8 with F2.
Important Points to Remember
A. Six hybrid orbitals are formed in SF6.
B. One 3s-orbital, three 3p-orbitals, and two 3d-orbital take part in the hybridization process of SF6.
C. The six sp3d2 hybrid orbitals are projected towards the six corners of a regular octahedron.
Golden Key Points
The shape of covalent molecules:
It was given by Sidgwick and Powel. According to this concept, the shape of covalent compounds depends on the total pairs of electrons present on the central atom, which is given below.