WAEC Chemistry 2010 Paper

Concept:In Group 17, physical state changes down the group because intermolecular forces strengthen.Explanation:At room temperature, chlorine ($\mathrm{Cl}_2$) has small molecules and weak van der Waals forces.So, chlorine exists as a gas.Iodine ($\mathrm{I}_2$) has larger molecules and much stronger van der Waals forces.Therefore, iodine exists as a shiny solid at room temperature.Thus, the correct statement is that chlorine is a gas and iodine is a solid.Answer:A. Chlorine is gas and iodine is solid