Which of the following molecules would have the strongest London Dispersion Force?

A. F²

B. Cl²

C. Br²

D. I²

Answer: D

Explanation:

London forces become stronger as the atom in question becomes larger, and to a smaller degree for large molecules. [4] This is due to the increased polarizability of molecules with larger, more dispersed electron clouds. The polarizability is a measure of ease with which electrons can be redistributed; a large polarizability implies that the electrons are more easily redistributed. This trend is exemplified by the halogens (from smallest to largest: F 2, Cl2, Br 2, I 2). The same increase of dispersive attraction occurs within and between organic molecules in the order RF
gases at room temperature, bromine is a liquid, and iodine is a solid. The London forces are thought to be arise from the motion of electrons.