At stp, fluorine is a gas and iodine is a solid. this observation can be explained by the fact that fluorine has
(1) weaker intermolecular forces of attraction than iodine
(2) stronger intermolecular forces of attraction than iodine
(3) lower average kinetic energy than iodine
(4) higher average kinetic energy than iodine

The answer is 4. The molecules of each material entice each other over dispersion (London) intermolecular forces. Whether a substance is a solid, liquid, or gas hinge on the stability between the kinetic energies of the molecules and their intermolecular magnetisms. In fluorine, the electrons are firmly apprehended to the nuclei. The electrons have slight accidental to stroll to one side of the molecule, so the London dispersion powers are comparatively weak. As we go from fluorine to iodine, the electrons are far from the nuclei so the electron exhausts can more effortlessly misrepresent. The London dispersion forces developed to be increasingly stronger.