What happens to the reactivity of Group 7 elements as you go down the group?

• A. Increases
• B. Decreases
• C. Remains the same
• D. Varies unpredictably

Answer: (B)

As you go down Group 7, reactivity falls because the halogen’s ability to gain an electron weakens. A halogen’s reactivity is tied to how strongly it can attract and accept an extra electron to become a halide ion. Moving to heavier members, the outermost electron is farther from the nucleus and more shielded by inner electrons, so the effective pull of the nucleus on that incoming electron lessens. That weaker attraction makes the reduction process harder, reducing reactivity. This is why fluorine is the most reactive, with reactivity decreasing through chlorine and bromine to iodine. The trend isn’t an increase, constant, or unpredictable; it shows a clear downtrend in reactivity due to larger atomic size and greater shielding.