Question
The 
-bond is weaker than carbon-carbon σ bond. Explain.
Solution
The >C = C< bond is made of σ bond and 
bond. The 
bond is weaker than σ bond because electron in the 
bond are more diffused in space i.e. orbitals participating in the 
bond formation overlap sidewise only to small extent. On the other hand, orbitals participating in the σ bond formation overlap axially to a greater extent.
The greater the extent of overlapping, the higher the probability of finding the valence electrons in between the nuclei and hence the bond will be stronger and shorter. Hence overlap in 
bond is less effective as compared to σ bond.
