The bonds in the SiCl₄ molecules will be more polar.
The polarity of bonds within a molecule depends on the difference in electronegativity of the atoms that are involved in the bond. Chlorine is a more electronegative atom than iodine. Therefore, the electrons in the Si-Cl bond will be more concentrated near the Cl, creating polarity in the bond. Iodine is not as electronegative, so it will not result in a very polarized Si-I bond
