INDUCED DIPOLE FORCES

Now lets think about intermolecular forces. There are three different forces, force between non-polar molecules, non-polar and polar molecules, and polar molecules.
Forces between non-polar molecules are the weakest of all intermolecular forces.
In the non-polar molecules there are 'Temporary dipoles" which are formed by the shifting of electron clouds within molecules. These temporary dipoles attract or repel the electron clouds of non-polar molecules.
The temporary dipoles exist for a fraction of a second, so a force of attraction exist for that fraction of time. The strength of induced dipole forces depends on how easily electron clouds can be distorted. Atoms or molecules which have many electrons are more easily distorted, because these electrons are far from their nucleus.
Okay, please explain about intermolecular forces in iodine molecules as shown in the picture. Give the reason why in the iodine molecule, atom that has the negative temporary pole is bigger than atom with positive temporary pole,