In the second period of elements, although oxygen lies next to nitrogen yet its ionization first energy is lower than that of nitrogen because?

Explanation

Option A is factually correct but has no bearing on ionization energy. Option B is factually correct as oxygen has one more proton in its nucleus than nitrogen, however, because of this, the ionization energy must increase, but in reality, the ionization energy of oxygen is lower than that of nitrogen. Option C is factually correct, but has no bearing on activation energy. Option D is correct because oxygen has 6 valence electrons compared to Nitrogen's 5 valence electrons so, the electronic configuration of the last shell of O is 2s2 2p4 compared with nitrogen's 2s2 2p3. In N, the p subshells have all three orbitals, singly filled with electrons whereby in oxygen, one p orbital has a pair of electrons. In this orbital, the two electrons exert repulsion which will lower the ionization energy due to a decrease in the effective nuclear force of attraction between the outermost electron and nucleus in the oxygen atom.