Question

(ii)Explain why ionization enthalpy of oxygen is less than nitrogen.

Answer 1

Electronic configuration for:

Oxygen(O): 1s²2s²2p⁴
Nitrogen(N): 1s²2s²2p³

Ionization Enthalpy is the energy required to remove loosely held electron from the valence shell of an atom.

For Oxygen, there are 6 electrons in the valence shell while for Nitrogen, there are 5 electrons in the valence shell. Also, we know that half filled and full filled orbitals are more stable. Here, electron in both atom ends in the p orbital. Also, in Nitrogen the orbital are half filled as there can be total of 6 electrons in p orbital.

Hence, the energy required to remove an electron from valence shell of Nitrogen requires more energy.

Thus, Nitrogen has more IE than Oxygen.

Answer 2

Answer:

(1) The electronic configuration of nitrogen (N, Z = 7) is 1s², 2s², 2p³ and that of oxygen (O, Z=8) is 1s², 2s² 2p^4.

(2) Nitrogen atom acquires extra stability due to half- filled 2p-orbitals while oxygen can acquire half-filled orbital and extra stability by losing one electron. Thus, oxygen can easily lose one electron.

(3) Nitrogen requires more energy to remove an electron due to extra stability. Therefore, first ionisation enthalpy of oxygen is less than that of nitrogen.