Which one is not correct statement?

Ionization energy(I) for nitrogen is less than that of oxygen.

As the number of electrons in an element's valence shell rises, the element gets bigger. According to what we can observe, the nitrogen atom will be more stable than the oxygen atom, since it has an atomic orbital that is only partially filled. In light of this, O has a lower initial ionization energy than N.

Hence, option D is correct.