Why do some metals have higher specific heats than others?

Interesting question. Note that there are several ways of measuring specific heat:

A. per unit mass

B. per unit molecule

C. per unit atom

If you measure per unit mass, Uranium (very dense) is at 0.116 J/kg/K while Lithium (not at all dense) is at 3.58.

But if you look at the numbers per mole, you get Uranium at 27.7 and Lithium at 24.8 - a much smaller difference

http://en.wikipedia.org/wiki/Specific_heat_capacit...

This is in accord with first order theory:

http://hyperphysics.phy-astr.gsu.edu/HBASE/thermo/...

But this still doesn't explain the more than 10% variation that remains. A couple of papers suggest that the difference is in the electrons:

http://adsabs.harvard.edu/abs/2000APS..TSF.B3003G

http://www.iop.org/EJ/abstract/0370-1328/81/4/313

That's all I know.