Question

Out of n2 and o2, which has greater bond dissociation energy and why

Answer 1

I think N2 has more bond dissociation energy. If you observe the structure of the the two molecules, you'll see that the nitrogen molecule links two atoms by a triple bond ( one Sigma and two pi) whereas oxygen has only a double bond. The bond energy is directly proportional to bond order, so since there are more bonds in nitrogen, it will posses more energy and has a higher dissociation energy.