I have been trying to get my head around this question, but do not understand it. Consider the two isoelectronic substances, bromine (Br2) and Iodine monochloride (ICl). Based upon your knowledge of intermolecular forces, explain the difference in their boilings pts. (Bromine: 59 degrees C; iodine monochloride: 97 degrees C) Well, I know that both bromine and iodine monochloride have 70 electrons per molecule, therefore, the strength of the London dispersion forces between the molecules of each should be the same. Now, what I'm not sure of is how to assess their polarities. VSPER Theory doesn't really help me out because they are both of the same shape, so one would assume that they would both be either polar or non-polar. However, if I assess their respective electronegativities... BR-BR (must be the same; therefore has to be non-polar?) I-CL (is different; therefore polar?) Therefore, ICL should have stronger dipole-diple-force, and a higher boiling point. Are these conclusions justified? Thanks for your prompt response.