C. Lead crystallizes in a face-centered cubic structure with a density of 11.34 g/cm3. Polonium crystallizes in a simple cubic structure with a density of 9.3 g/cm3. Explain why lead has a greater density than polonium even though polonium atoms are heavier, and smaller than lead atoms.

Because of their differences in their crystal systems, lead is more densely packed.

Explanation:

In a face-centered cubic structure, there's a total of 4 atoms per unit cell ( 1/8 * 8 atoms in the corners, plus 1/2 * 6 atoms in each of the faces). This also means that in each cube, each atom is surrounded by 12 other atoms.

While in a simple cubic structure, there's a total of only one atom per unit cell (1/8 * 8 atoms in the corners).

i'm pretty sure its b i might be wrong though!