Why is the electron affinity for nitrogen positive?

1 Answer
Dec 7, 2015

Since we typically expect electron affinity to be negative except for certain exceptions like Nitrogen, this is one of those exceptions.

Nitrogen's electron configuration is #1s^2 2s^2 2p^3#, so all three #p# orbitals have one electron each.

Since electron affinity is associated with the "love" for acquiring another electron, and the new electron would be added in one of the singly-occupied #p# orbitals, we have a problem.

Each singly-occupied #p# orbital already has one electron, so that electron, clearly identical to the electron being added in every way---INCLUDING CHARGE---will repel the incoming electron, so more energy than usual is needed to add it.

This extra energy needed to overcome the repulsion makes the electron affinity positive.