Assertion : When the added electron goes to smaller n=3 quantum level, the electron- electron repulsion is much less.

Reason: The added electron occupies a smaller region of space .

It is due to low volume of electron that causes large distance between two electrons.

When the added electron goes to smaller quantum level, the repulsive force between two electrons is less because the electron which is added occupies small space due to less volume so there is a large distance between two electrons that leads to less force of repulsion.

If the electron has more volume so it occupies more space and there will more repulsive force between two electrons so that's why we can say that the smaller volume of electron is the reason of less repulsive force.