Question

What intermolecular forces exist in the halogens?

Answer 1

`"Dispersion forces......"`

Explanation:

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, `Cl_2` are room temperature gases. Bromine, `Br_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.