The enthalpy of fusion of a substance is the energy required to change the state of a substance from solid to liquid at a constant temperature. The enthalpy of fusion for iodine, Iā, will be higher. This is because there are stronger intermolecular forces holding the iodine molecules together. The stronger intermolecular forces arise from the fact that iodine is a much larger molecule, so it has much more electrons resulting in higher Van der Waal's forces. This is also visible in the fact that at room temperature, iodine is a solid while nitrogen is a gas.
