Correct Answer: half-filled P-orbitals

Solution : The correct option is half-filled P-orbitals.

Nitrogen, with its atomic number 7, has an electron configuration of 1s² 2s² 2p³. This means it has three electrons in its p-orbitals. The p-orbitals can hold a maximum of six electrons, and having three electrons in the p-orbitals results in them being half-filled. This half-filled configuration provides additional stability to the nitrogen atom, which contributes to its higher ionization energy compared to oxygen.