Chemistry - PERIODIC TABLE Question with Solution | TestHub

The correct characteristic is D. The second ionization energy order is $N<O$. Nitrogen has a stable half-filled 2p subshell after losing one electron ($N^{+}:[He]2s^{2}2p^2$), making it easier to remove the second electron compared to oxygen ($O^{+}:[He]2s^{2}2p^3$), which has a more stable half-filled 2p subshell after losing one electron.