Consider ethene molecule
1. In the formation of CH2 – CH2 each carbon atom in its excited state undergoes sp2 hybridisation by intermixing one s-orbital (2s) and two p-orbitals (say 2px and 2py ) and reshuffling to form three sp2 orbitals.
2. Mow each carbon atom is left with one ‘p’ orbital (say 2pz) unhybridised.
3. The three sp2 orbitals having one electron each get separated around the nucleus of carbon atoms at an angle of 120°.
4. When carbon is ready to form bonds one sp2 orbital of one carbon atom overlaps the sp2 orbital of the other carbon atom to form sp2 – sp2 sigma (σ) bond.
5. The remaining two sp2 orbitals of each carbon atom get overlapped by ‘s’ orbitals of two hydrogen atoms containing unpaired electrons.
The unhybridised pz orbitals on the two carbon atoms overlap laterally as shown in figure to form a π (pi) bond.
6. Hence, there exist a sigma (σ) bond and a pi π (pi) bond between two carbon atoms in ethene molecule. Hence, the molecule ethene (C2H4) is
