# What intermolecular forces exist in the halogens?

$\text{Dispersion forces......}$
The halogens are the only Group of the Periodic Table that displays gaseous, liquid, and solid forms of the elements at normal temperatures and pressures. Fluorine, ${F}_{2}$, and chlorine, $C {l}_{2}$ are room temperature gases. Bromine, $B {r}_{2}$, is a room temperature liquid. And iodine, ${I}_{2}$, is a volatile, room temperature molecular solid.
Why should iodine be a solid? Well, the halogens have dispersion forces as the only intermolecular force of attraction. As the molecule, ${X}_{2}$, gets bigger, and the electron cloud correspondingly gets bigger with greater $Z$, there should be a greater force of intermolecular interaction as the electron becomes more polarizable. And this is manifested by the state of each element: which is SOLID for iodine under normal conditions.