Question

Identical spheres are undergoing two-dimensional packing in square close packing and hexagonal close packing. Which of the following statements are correct regarding the spheres?

• A. The ratio of coordination number for a sphere in first case to that in second case is $2:3$.
• B. Packing in second case is more effective.
• C. Packing in first case is more effective.
• D. The stacking of layer on first type packing produces simple cubic structure.

Answer 1

Answer: (A), (B), (D)

Packing in second case is more effective.
The stacking of layer on first type packing produces simple cubic structure.
The ratio of coordination number for a sphere in first case to that in second case is $2:3$.

In square close packing, coordination number $=8$, whereas in hcp, coordination number $=12$. So, the ratio is $2:3$.