Bond length/Intermolecular Forces

[Darlab_3A]

I’m a little confused on the relationship between polarizability, bond strength, and intermolecular forces. I understand that the larger an anion/element acting as a negative dipole moment, the more polarizable, and therefore the stronger the induced-dipole induced-dipole interactions because it is more polarizable. This would cause compounds to have higher melting points, as there are stronger forces. There is also the idea that the larger the element, the weaker the bond because there is more distance. This is contradictory, as longer bonds would break more easily and I would think this would lower the melting point. I2 for example is said to be a solid at room temperature while Cl2 is a gas due to the induced dipole forces, although I would think that since the I element is much bigger it would have a weaker bond. If anyone could explain this I would really appreciate it.

[Nicole Coulter]

So what you are getting confused (something that I also got confused on originally), is the difference between intermolecular and INTRAmolecular forces. The strength of the bond between the two Iodines is an Intramolecular force, versus the forces between two I2 molecules interacting with each other. If the words are not a good explanation, its like between two I2, like (I-I)-(I-I), where the dash between the two molecules is the INTERmolecular force. But you are correct that the INTRAmolecular forces between Cl-Cl would be stronger than I-I because of bond length due to atomic radii.