I've been collecting data and there's a very strong inverse relationship between electronegativity difference and density ($\pu{R^2}$ value of roughly 0.95 from my data). Is there any chemistry that could explain these results?
This doesn't make much sense to me because I would have thought increasing electronegativity difference would result in more polar bonds and thus more polar molecules, which would result in stronger inter-molecular forces and thus smaller volume (and hence more mass being packed into a smaller volume).