How does the shielding effect influence the periodic properties of elements within a group in the periodic table?

The shielding effect means that inner‑shell electrons block the pull of the nucleus on outer electrons, so the outer electrons feel a weaker effective nuclear charge. In a group, each element adds one more electron shell, increasing both the number of shielding electrons and the distance from the nucleus. Because the shielding grows, the outer electrons are held less tightly, which makes the atomic radius larger, the ionization energy lower, and the electronegativity smaller as you go down the group. For example, sodium’s outer electron is pulled more strongly than potassium’s, so sodium has a smaller radius, higher ionization energy, and higher electronegativity than potassium. This systematic change is a direct result of the increasing shielding effect within the group.