Final answer:
It is easier to remove a 2p electron from an oxygen atom than from a nitrogen atom because oxygen has a paired electron in its 2p orbitals. This paired electron experiences repulsion, making it less tightly bound, and removing it results in a stable, half-filled sublevel.
Step-by-step explanation:
The ease of removing an electron from an oxygen atom compared to a nitrogen atom can be explained by the electronic configurations of these elements and Hund's rule. Oxygen, which is in Group 16, has a 2p electron configuration of 1s²2s²2p⁴, meaning that one of its 2p orbitals contains a paired set of electrons. Nitrogen, in Group 15, has a 2p electron configuration of 1s²2s²2p³, with each 2p electron in a separate orbital. According to Hund's rule, electrons will fill an empty orbital before pairing up. In oxygen, the electron-electron repulsion between the paired electrons in the same orbital makes it slightly easier to remove one of them. This is due to the repulsion between electrons in the same orbital, making them slightly less tightly bound to the nucleus. Additionally, removing a paired electron from oxygen will result in a more stable, half-filled sublevel, which is energetically favorable compared to removing an unpaired electron from nitrogen, which already has a half-filled sublevel.