Hybridisation is the process of intermixing atomic orbitals of almost similar energies to form new orbitals of equal energy and identical shape. Here, we will discuss about the valence bond theory to understand the concept of hybridisation.
What is Hybridisation
It is the process of intermixing atomic orbitals of almost similar energies to form new orbitals of equal energy and identical shape. The new orbitals formed are hybrid orbitals.
Important conditions to form Hybrid orbitals
- Only orbitals having almost equal energies belonging to same atom/ion can participate in the process.
- The orbitals present in the valence shell of the atom are undergoing process.
- Promotion of electron is not the essential condition.
- Even completely filled orbitals in addition to half filled orbitals can undergo the process.
Salient features to form Hybrid orbitals
- Number of hybrid orbitals formed are equal in number of atomic orbitals mixing.
- The bigger lobe of the hybrid orbital has +ve sign while the smaller lobe has -ve sign.
- Hybridised orbitals are always equivalent in energy and shape.
- The hybridised orbitals form more stable bonds than pure atomic orbitals.
- It occurs at the time of bond formation.
- It indicates the geometry of the molecule.
Types of Hybridisation
- Diagonal or Sp hybrid^n
Sp hybridisation is the intermixing of one s and one p orbital of same shell to form 2 new equivalent orbitals. For example: BeF2, BeH2, C2H2. Sp hybridised orbitals has 50%- s and 50%- p character. The 2 hybridised orbitals are collinear with an angle of 180 degrees. The remaining two p orbitals which do not participate in bond formation remains as such.
- Trigonal or Sp2 hybrid^n
Sp2 hybridisation is the intermixing of one s and two p orbitals of same shell to form 3 new equivalent orbitals. All the 3 hybrid orbitals makes an angle of 120 degree. Sp2 hybridised orbital has 33 % s character and 67% p character. For example : BF3, BH3, C2H4 etc.
- Tetrahedral or Sp3 hybrid^n
Sp3 hybridisation is the intermixing of one s and 3 p orbitals of same shell to form 4 new equivalent orbitals. These 4 hybrid orbitals are directed towards the corner of a tetrahedron at an angle of 109 degree 28 minutes. Each sp3 hybridised orbital has 25% s character and 75 % p character. For example : CH4, C2H6 etc.
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