Question

Give reasons for the following:
N-N bond is weaker than P-P bond.

Answer 1

The nitrogen atom is smaller in size than the Phosphorus atom. The bond length of the N-N bond is smaller than that of the P-P bond. Due to this, the four non-bonding electrons of the two nitrogen atoms repel each other making the bond weaker.
This does not happen in the case of phosphorus because P-P bond length is more. So, the repulsion of non-bonding electrons is lesser than in N-N. So, the P-P sigma bond is stronger.