[toeknee2120]

In my class, we go with the generalization that if a polar molecule has a mass less than 30g greater than a non-polar molecule, the dispersion forces from the non-polar molecule are greater than the dipole and dispersion forces from the polar molecule.

ex. Which has stronger Intermolecular Forces (IMF), CCl₄ or HBr? HBr is polar and has a mass ≈ 80g/mol, but CCl₄ (though non-polar) has a mass ≈ 152 g/mol, so it has stronger IMF.

Is there a similar rule for ionic compounds, or are they ALWAYS stronger than non-polar and polar molecules? For example, is the IMF in CCl₄ greater than LiF?

[Dan]

For example, is the IMF in CCl₄ greater than LiF?

Ionic compounds are not molecular, so it does not really make sense to talk about intermolecular forces for LiF.

Compare the boiling points of CCl₄ and LiF.