Compare the packing efficiency of face-centered cubic aluminum and face-centered cubic lead.
A) The efficiency of packing in the aluminum unit cell is higher because the aluminum atom is larger.
B) The efficiency of packing in the lead unit cell is higher because the lead atom is larger.
C) The efficiencies of packing in the unit cells of these two metals are the same.
D) The efficiency of packing in the aluminum unit cell is higher because the aluminum atom is smaller.
E) The efficiency of packing in the lead unit cell is higher because the lead atom is smaller.

Question

Quizplus · Accepted Answer

Face-centered cubic (FCC) unit cells of both aluminum and lead have the same packing efficiency. In an FCC structure, each atom is surrounded by 12 nearest neighbors, forming a regular octahedral arrangement. The edge length of the unit cell for aluminum is 4.05 Å, and that for lead is 4.95 Å. However, since both metals have an atomic radius around 1.43 Å (aluminum) and 1.45 Å (lead), the packing efficiency in their respective FCC structures is the same, which is about 74%.

Compare the Packing Efficiency of Face-Centered Cubic Aluminum and Face-Centered