Beryllium, magnesium and calcium are all elements in Group 2 of the periodic table. Explain why the reactivity of these elements increases going down the group.

Beryllium, magnesium and calcium are all Group 2 elements, so they each have two valence electrons. As you move down the group the atoms gain an additional electron shell, increasing the atomic radius. The outer 2s electron is therefore further from the nucleus and is shielded by more inner‑shell electrons. Consequently the electrostatic attraction between the nucleus and the outer electron is weaker. Because the outer electron is less tightly held, it is lost more easily, so the element forms ions more readily and reacts more readily. This explains the increase in reactivity down the group.