Between I2 molecules, the predominant type of force is known as Van der Waals forces, specifically London dispersion forces.
These are weak intermolecular forces that arise due to temporary fluctuations in the electron distribution within molecules. In I2, which is a diatomic molecule composed of two iodine atoms, the electron cloud can momentarily become unevenly distributed, creating a temporary dipole. This dipole can induce a similar dipole in a neighboring I2 molecule, leading to an attraction between them.
While these forces are relatively weak compared to covalent or ionic bonds, they play a crucial role in the physical properties of iodine, such as its state at room temperature. Iodine exists as a diatomic molecule and is a solid due to these intermolecular forces, which, although weak, allow the molecules to remain associated in the solid form.