Question

The trend is increasing ionisation enthalpy from left to right, but first IE of Oxygen is lower than Nitrogen.
Give reason.

Plz ans fast plzzz ​

Answer 1

Oxygen also has an unexpectedly low ionisation energy, less than that of nitrogen. This is due to an electron being added to an already half full orbital in oxygen, which results in electron electron repulsion, which will lower the ionisation energy.