Why the ionization energy of nitrogen is more than oxygen?

• Ionization energy: Ionization energy is defined as the minimum energy required to remove loosely bounded electron from an isolated gaseous atom.
• As we know, nitrogen belongs to group-15 while oxygen belongs to group-16 due to which oxygen should have more ionization energy but nitrogen has more ionization energy than oxygen. This is due to the electronic configuration of nitrogen and oxygen.
• $$\begin{gathered} N(atomicnumber=7)=1s^{2}2s^{2}2p^3 \\ O(atomicnumber=8)=1s^{2}2s^{2}2p^4 \end{gathered}$$
• Nitrogen contains a half-filled configuration which is extra stable than oxygen.
• Hence, the ionization energy of nitrogen is more than oxygen.