63.CHEMICAL BONDING (10)- Covalent Bonding(9)- sp2 Hybridization(4).

sp2 hybridization .

The process of mixing of one s- orbital with two p- orbitals in an atom to form three sphybrid orbitals of equivalent energy is called sphybridization.



In ethene molecule, the central carbon atom is sp2 hybridized.
Carbon (6)  in ground state 1s2 2s2 2p2
One 2s electron is promoted to 2p orbital→ C(6)  1s2 2s2p
Then, 2s and two 2p hybridize to form three sp2 hybrid orbitals.




Two sp2 hybrid orbitals of each carbon atom overlap to form  sp2 – sp2 bond.This is the sigma bond between two carbon atoms.
However, in this case , a π bond is formed too.The unhybridized porbitals (the p-orbitals which DO NOT take part in hybridization) of both the carbon atoms lie perpendicular to the hybridized orbitals. They overlap laterally/sideways to form a π bond.


The unhybridized p orbital lobes, which overlap laterally to form one π bond , are shown in pink  color in the following figure –

pie bond 1 .jpg


NOTE – i)Diagrammatically, the π bond is always shown above and below the sigma bond.Though its shown in two places(these are two regions where p orbital lobes overalp) it symbolizes one π bond only. The two regions show that the electron cloud is above and below the bond axis.



The ethene molecule is formed with 4 hydrogen atoms. As we already know that the electron in hydrogen atom is in 1s orbital.Thus, this is a    sp2– s overlap.




Pictorially the above bonds can be shown as follows –



NOTE – The three hybrid orbitals point towards the corners of a triangle at 120o to each other.They all are in the same plane – in the plane of the bond axis.The pz orbitals are perpendicular to the bond axis.

sp2 hybridization occurs when a carbon atom is attached to 3 groups.In the above example each carbon atom is attached to two hydrogen atoms and another carbon atom.

A sp2  hybrid orbitahas 33% s character and 67% p character.

In our next post we shall discuss sp hybridization. Till then,

Be a perpetual student of life and keep learning..

Good day.

References and further reading –

  1. http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch02/ch2-3-2.html
  2. https://courses.lumenlearning.com/introchem/chapter/sp2-hybridization





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