Question

among nitrogen and oxygen which element has more first ionization energy?why?

Answer 1

Nitrogen has extra stability due to its half filled 2p orbitals. It has 1s2 2s2 2p3 configuration and hence its electron is a little more difficult to extract as compared to oxygen atom which has 2p4 configuration.

Answer 2

nitrogen has more ionisation energy.
nitrogen has half filled 2p orbital... so it gains an extra amount of stability.. whereas oxygen has 4 electrons in 2p orbital which is neither half filled nor fully filled... hence more energy is needed to knock out electrons from the orbitals of n2 than o2.... so n2 has got more ionisation energy