WAEC Chemistry 2015 Paper

Concept:In Group 17, the physical state of halogens changes down the group from gas to liquid to solid because of increasing intermolecular forces.Explanation:At room temperature, fluorine ($\mathrm{F_2}$) and chlorine ($\mathrm{Cl_2}$) exist as gases.Bromine ($\mathrm{Br_2}$) is the only halogen that exists as a liquid at room temperature.Iodine ($\mathrm{I_2}$) is a dark, crystalline solid at room temperature.Larger molecules like iodine have stronger dispersion forces, which hold the particles closely in a solid lattice.Therefore, among the given halogens, iodine is the one that remains solid at room temperature.Answer:D. Iodine