O vs N [ENDORSED]

[Noh_Jasmine_1J]

why does Oxygen have lower ionization energy than Nitrogen ?

[Mayaal_Khan_4H]

Ionization energy increases across a table because the valence shell of the elements as you go towards the right is nearly filled whereas as, as you go towards the left, the electrons have a low ionization energy from their willingness to lose electrons and become cations which is why Oxygen has a lower ionization energy than Nitrogen.

[rosemarywang4i]

It's because nitrogen's p orbital is half filled, so it's more stable than oxygen and thus requires more energy to remove an electron.

[jonathanjchang2E]

The fourth valence electron in oxygen's p orbitals has a lower ionization energy because of the electron electron repulsion formed by the lower three valence electrons. This ionization energy is lower than nitrogen because of the three parallel electrons in nitrogen's p orbitals.

[Katie Frei 1L]

Oxygen has a lower ionization energy because, even though it is technically further down the period than Nitrogen, its p orbital is half-filled, making it more stable and so harder to remove an electron.