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 atomic orbitals at approximately equal energy and redistribution of energy to form new orbitals, 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 the Be Cl₂ compound. If it is formed without hybridization then both the Be---Cl bonds 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 consider 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 strength of both the bonds will be equal.
Characteristic of Hybridization
Hybridization is a process of mixing of orbitals and not electrons. Therefore in hybridization full-filled, half-filled, and empty orbitals may take part. The number of hybrid orbitals formed is always equivalent to the number of atomic orbitals that 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 is equal to the number of sigma bond + lone pair of electrons. The 1st bond between two atoms will be a sigma bond. The other bond between the same two atoms will be the 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, Carbon that exhibits 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 pairs of electrons around the central atom:
Method 2: To predict hybridization the 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 in BrF3 (Bromine Trifluoride)
We can determine the hybridization process in BrF3 by taking bromine as a central atom. The electronic configuration of Br is represented as 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5. Bromine will form bonds with fluorine atoms and due to bond formation, some of the electrons of bromine will be shifted to 4d-orbitals. Due to the higher oxidative capacity of fluorine, it forces bromine to promote electrons to the given level. After this, bromine can use the d-orbital hybridization.
Hybridization of BrF3 can be determined by taking bromine as a central atom and three valence shells of bromine get bonded with three fluorine atoms as fluorine has seven electrons in the outermost shell and they need one electron to complete the octet rule and after hybridization they will further have 2 lone pairs of electrons left. So from this concept, the hybridization value or the electron pair is equal to 5 it gives rise to sp3d hybrid orbitals.
Important Points to be Remembered in BrF3 (sp3d Hybridization)
The central atom uses d-orbital for the hybridization process.
Two lone pairs and three Br--F bond pairs are there in BrF3.
The nature of the bond is covalent.
Lone pairs also take part in the hybridization process.
Geometry and Bond Angle of BrF3
BrF3 has three bonded and two non bonded electrons, which gives it a trigonal pyramidal geometry and a T-shaped molecular structure. Their bond angles are a little compressed when we compare it to normal trigonal bipyramidal structure and this compression in bond angle is due to lone pairs spreading out more in space than the bonded pairs. The bond angle in BrF3 is slightly lesser than 900. And the reason behind the lower bond angle is due to the lone pair-bond pair repulsion, so the accurate measure of the bond angle of BrF3 is 860.