Question

Which of the following represents the closest packed arrangement of uniform solid spheres:

• A. Simple cubic unit cell
• B. Body - centred cubic unit cell
• C. Face centered cubic unit cell
• D. Hcp unit cell

Answer 1

Answer: (C), (D)

Hcp unit cell

The packing efficiency of the simple cubic unit cell is $52\%$ and of bcc is $68\%$.
Packing efficiency of face centred cubic unit cell and hcp is $74\%$.
Since, the packing efficiency of face centred cubic unit cell and hcp is maximum and so, they represent the closely packed arrangement of uniform solid spheres.