Another 2 questions......?

Question

1. What is shielding?

2. Explain how shielding contributes to the atomic radius trend within a group.

Answer 1

1. Shielding is the tendency for the inner electrons to "shield" the outer (or valency) electrons from some of the positive charge of the nucleus.

2. Because the valency electrons are not held with as much force as they would be without shielding, they are further away from the nucleus.

Therefore, as you go down a group of the periodic table, atomic radius increases.