Which element would most likely pull in electrons during formation of a compound sb, i, CI

The answer is I. I (Iodine) has a larger mass number in its nucleus hence its electron orbital shells are pulled more towards the nucleus than in the other elements. Therefore, even in molecules formed involving iodine atoms, iodine will be more electronegative (have a negative dipole), because it will pull most of the electron cloud of the molecule towards it.