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Hybridisation is the concept of mixing atomic orbitals into new hybrid orbitals with different energies, shapes etc. than the actual orbitals. It is well understood by the following example.

Carbon shows tetravalency

S and P orbital belongs to the same atom having slightly different energies mix together to produce same number of new set of orbital called as hybrid orbital and the phenomenon is called as hybridisation.

Important characteristics or features of hybridisation:-

  (i) The number of hybridised orbital is equal to number of orbitals that get hybridised.

  (ii) The hybrid orbitals are always equivalent in energy and shape.

  (iii) The hybrid orbitals form more stable bonds than the pure atomic orbital.

  (iv) The hybrid orbitals are directed in space in same preferred direction to have some stable arrangement and giving suitable geometry to the molecule.

Types of hybridisation

(i) sp³ hybridisation : In this case, one 's' and 3'p' orbitals hybridise to form four sp³ hybrid orbitals. The four sp³ hybrid orbitals are oriented in a tetrahedral arrangement.

For example : In methane CH₄

(ii) sp² hybridisation : In this case one s and two p orbitals mix together to form three sp² hybrid orbitals are oriented in a trigonal planar geometry.

The remaining p orbital if required form sideways overlapping with the other unhybridised 'p' orbital of other 'c' atom and leads to the formation of = bond as in CH₂ = CH₂

The remaining two unhybridised p orbitals overlap  with the another unhybridised 'p' orbital leading  to the formation of triple bond as in .

2. Trigonal planar               sp²

3. Tetrahedral                     sp³

4. Trigonal bipyramidal      sp³d

5. Octahedral                      sp³d²

6. Pentagonal bipyramidal  sp³d³