Why does Oxygen have a lower first ionization than both nitrogen and flourine

[Kainath Kamil Dis 2K]

Isn't oxygen more electronegative than nitrogen? Why is it easier to remove an electron from oxygen compared to nitrogen?

[Ryan Burchell 3D]

I think it has to do with Oxygen having a pair in its p orbital that nitrogen does not have. The paired electron that oxygen has experiences electron-electron repulsion and therefore it is easier ionized.

[Reece Fong 2k]

If you read the solution for number 24 on the achieve homework, it states that electron-electron repulsion is responsible for oxygen having a lower first ionization energy than nitrogen. This is because it's less stable for two electrons to be in the same orbital due to that repulsion. For fluorine, the electron simply experience a higher effective nuclear charge (more protons = less radius). The electron-electron repulsion wouldn't apply in this case because flourine also has orbitals that are filled with 2 electrons in the 2p subshell.

[HannahArabi14a]

WE will find that oxygen will have a lower ionization energy level compared to nitrogen, because an electron from oxygen is being added to what is already a half of a full orbital. What occurs from this added electron is the result of an electron repulsion that then lowers the ionization energy as a result. The difference between oxygen and nitrogen orbitals is that oxygen has 2p orbitals that can be paired electrons that could be removed, while nitrogen doesn't have this ability.

Hope this helps!

[kylanjin]

Oxygen would have a lower IE than N because it has more electron repulsion due to the extra electron in the p orbital. Oxygen having a higher IE than fluorine follows the general trend of IE across a period as atoms get more electronegative and therefore are less willing to give up electrons. Because fluorine also has a smaller atomic radius than oxygen, its effective nuclear charge is stronger, making it harder to pull an electron off and therefore giving it a higher IE.

[Muryam_Hasan_2I]

The pair of electrons in the 2p orbital of oxygen creates an electron-electron repulsive force greater than the singular electron in nitrogen could. Fluorine, on the other hand, has a lower ionization energy based on the general periodic trend and its higher effective nuclear charge.