What happens to the reactivity of Group 1 elements as you go down the group?

• A. It decreases
• B. It stays the same
• C. It increases
• D. It first increases then decreases

Answer: (C)

As you move down Group 1, reactivity increases. The outermost electron is farther from the nucleus and more shielded by inner electrons, so the attraction the nucleus exerts on that valence electron weakens. That means it requires less energy to remove the outer electron, i.e., the ionization energy decreases. With lower ionization energy, the atom can lose its single valence electron more readily in chemical reactions, making it more reactive. In practice, elements like lithium react with water, but down the group the reactions become progressively more vigorous as you go to sodium, potassium, rubidium, cesium, and the heavier alkali metals.