Question

Draw diagrams showing the formation of a double bond and a triple bond in ethene and ethyne

Answer 1

Answer:

C2H4 :

The electronic configuration of C-atom in the excited state is

C has 4 unpaired electrons in the valence shell,therefore in the formation of C2H4 , each Carbon atom undergoes sp2 hybridization leaving 2pz orbital unhybridized

One sp2 hybrid orbital of one carbon overlaps with sp2 hybrid orbital of other carbon atom to form sigma c---c bond.Now the unhybridized 2pz orbital of one carbon atom overlaps sidewise with similar orbital of the other carbon atom to form pie bond.The remaining 2 sp2 hybrid orbitals of both carbon atoms overlap axially with the half filled 1s orbitals of hydrogen atom forming C---H sigma bond

C2H2 :

Here both the carbon atoms undergoes sp hybridization leaving 2 unhybridized (2py & 2pz) orbitals.One sp hybrid orbital of one carbon atom overlaps axially with sp hybrid orbital of other carbon forming C----C sigma bond. The two unhybridised orbital of one carbon overlaps sidewise with similar orbital of other carbon atom to form two pie bonds. The remaining hybrid orbitals of each carbon overlaps axially with half filled orbitals of Hydrogen forming sigma bond.