Here's why:

* London Dispersion Forces: Both F₂ and Cl₂ are nonpolar molecules, so the only intermolecular forces they experience are London dispersion forces. These forces arise from temporary fluctuations in electron distribution within the molecule, creating temporary dipoles.

* Size and Polarizability: Chlorine atoms are larger than fluorine atoms. Larger atoms have more electrons, and these electrons are further from the nucleus. This makes them more polarizable, meaning their electron clouds can be more easily distorted to create temporary dipoles.

* Strength of London Dispersion Forces: Larger, more polarizable molecules have stronger London dispersion forces. Since Cl₂ is larger and more polarizable than F₂, its London dispersion forces are stronger.

In summary: The stronger London dispersion forces in Cl₂ due to its larger size and greater polarizability make it have stronger intermolecular forces than F₂.