At 20°C, the density of copper is 8.9 g/cm^3. The density of platinum is 21.4 g/cm^3. What does this tell you about how the atoms are "packed" in each material?

Feb 18, 2016

Good question. Remember, that we compare a 3rd row transition metal $\left(P t\right)$, to a 1st row transition metal $\left(C u\right)$.
$\text{Molar mass (Cu)}$ $=$ $63.55$ $g \cdot m o {l}^{-} 1$.
$\text{Molar mass (Pt)}$ $=$ $195.08$ $g \cdot m o {l}^{-} 1$.
This threefold difference in molar mass, of course translates to atomic mass. 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 density, $\text{mass per unit volume}$. Does this make sense?