What is the electron configuration of the oxide anion O2−?

Question

What is the electron configuration of the oxide anion O²⁻?

Answer 1

Let's look at the electron configuration of O first.

1s²2s²2p⁴ ... electron configuration for O

Since the oxide anion has a 2- charge, this indicates that O has GAINED 2 electrons. Where will they go?

There is still room in the 2p orbital, so electron configuration for O2- would be...

1s²2s²2p⁶