Good question. Remember, that we compare a 3rd row transition metal ##(Pt)##, to a 1st row transition metal ##(Cu)##.
##”Molar mass (Cu)”## ##=## ##63.55## ##g*mol^-1##.
##”Molar mass (Pt)”## ##=## ##195.08## ##g*mol^-1##.
This threefold difference in molar mass, of course translates to . Given that the difference in densities is (very approx.) threefold as well, we would predict that the atomic packing in both metals is similar in terms of , ##”mass per unit volume”##. Does this make sense?
