Hybridization : Salient Features, Type, Example

HYBRIDISATION

Hybridization is the concept of intermixing of the orbitals of an atom having nearlythesameenergytogiveexactlyequivalentorbitalswithsameenergy,identical shapes and symmetrical orientations in space.

The new equivalent orbitals formed are known as the hybrid orbitals or hybridized orbitals. Hybrid orbitals have properties entirely different from the

properties of the original orbitals from which they have been obtained.

Salient Features regarding Hybridisation

1.           Orbitals involved in hybridization should have nearly the same energy.

2.           The orbitals of one and the same atom participate in hybridization.

3.           The number of hybrid orbitals formed is equal to the number of hybridizing orbitals.

4.           The hybrid orbitals are all equivalent in shape and energy.

5.           A hybrid orbital which is taking part in bond formation must contain one electron in it.

6.           Due to the electronic repulsions between the hybrid orbitals, they tend to remain at the maximum distance apart.

7.           The head on overlap of atomic orbitals give sigma (s) bonds.

8.           The sidewise or lateral overlap of atomic orbitals give pi (p) bonds.

Tips to Predict the Type of Hybridisation in a Molecule or Ion (Other than Complex Ions)

Step 1 : Add the number of valence electrons of all the atoms present in the given molecule/ion.

Step 2 : In case of a cation, subtract the number of electrons equal to the charge on the cation and in case of an anion, add number of electrons equal to the charge on the anion.

Step 3 : (i) If the result obtained in step 2 is less than 8, divide it by 2 and find the sum of the quotient and remainder.

(ii) If the result obtained in step 2 lies between 9 and 56, divide it by 8 and find the first quotient (Q1). Divide the remainder R1 (if any) by 2 and find the

second quotient (Q2). Add all the quotients and the final remainder (R2). 

Let the final result obtained in (i) or (ii) be X. The type of hybridisation is decided by the value of X as follows :

Value of X  : Type of hybridization

2   :    Sp

3   :    sp2

4   :    sp3

5   :    sp3d

6   :    sp 3 d 2

7   :    sp3d3

Example

i)  BeCl2

Total valence electrons = 2 + 7 × 2 = 16

16 / 8 = 2(Q₁ ) + zero(R₁) ; X=2

 Hybridisation = sp

ii)  BF3

Total valence electrons = 3 + 7 × 3 = 24

24 / 8 = 3(Q₁ ) + zero(R₁) ;  X=3

Hybridisation in some Typical Molecules and Ions

Hybridisation

sp        -     Be F2, BeCl2, C2H2, CO2

sp2            -  SO2, BH3, BF3, NO2-, NO3-, CO32-    

 sp3        -  NH3, H2O, CH4, CCl4, SiCl4, H3O+,NH4+, ClO2-, ClO3-, ClO4-,NF3

sp3d        -    PCl5, ClF3, SF4, XeF2 

sp3d2        -    SF6, XeF4, XeOF4, BrF5

sp3d3        -     IF7, XeF6