Question

Second Ionisation energy of oxygen is higher as compared to nitrogen

Answer 1

To get a better understanding of second ionisation enthalpies we must have a look at their electronic configurations, which are -

O 2s2 2p4

N 2s2 2p3

Since the after removing one electron O will achieve a stable electronic configuration of 2s2 2p3, greater energy will be required and thus it will have more second ionisation enthalpy.