WAEC Chemistry 2016 Paper

Concept:Halogen reactivity decreases as we move down Group 17.Explanation:Halogens are non-metals in Group 17. As we move down the group, the atomic radius increases. The outer shell electrons are farther from the nucleus. This weakens the attraction between the nucleus and an incoming electron. So the ease of gaining an electron decreases. Hence reactivity decreases from fluorine to iodine: $\mathrm{F_2} > \mathrm{Cl_2} > \mathrm{Br_2} > \mathrm{I_2}$.Answer:The increasing order of halogen reactivity is $\mathrm{I_2} < \mathrm{Br_2} < \mathrm{Cl_2} < \mathrm{F_2}$.