go to this link of wikkipedia and see all the enthalpies (i mean 1st,2nd,3rd,.......)

https://en.m.wikipedia.org/wiki/Ionization_energies_of_the_elements_(data_page)

It is natural to expect that oxygen has a higher ionisation energy than nitrogen due to the fact that the first ionisation energy increases across a period. This is because when moving from left to right, the atomic number increases which means that the nuclear charge increases. As a result, the valence electrons are held more tightly to the nucleus and hence we expect the first ionisation energy to increase across the group.

But this trend is not followed when moving from nitrogen to oxygen. Wikipedia tells me that the first ionisation energies of nitrogen and oxygen are 1402.3kJ mol−1and 1313.9kJ mol−1respectively. Ionisation energy of nitrogen is found to be greater than oxygen

Electronic configuration of Oxygen is

1s2 2s2 2p4

Electronic configuration of Nitrogen is

1s2 2s2 2p3

You must be knowing that an atom containing half filled or fully filled orbitals are very stable. Nitrogen has a half filled 2p orbital. So when it is already stable, why would it want to lose an electron upon supplying energy and become unstable? This is why one requires large amounts of energy to ionised the nitrogen atom.

On the other hand, since Oxygen is already unstable relative to Nitrogen, by losing one electron it attains a stable half filled 2p orbital. So oxygen undergoes ionisation at a relatively lower energy. This is why nitrogen has a higher ionisation energy than oxygen.

electronic configuration of oxygen is

1s2 2s2 2p4

electronic configuration of nitrogen is

1s2 2s2 2p3

I am not asking between oxygen and nitrogen but in between fluorine and nitrogen

no matter the concept is same and please go through the link provided in order to see the values of any element