Question

Arrange the following crystal structures in ascending order of their coordination number.
A. Diamond
B. Sodium Chloride
C. Cesium Chloride
D. Zinc with hexagonal closed packed structure
Choose the CORRECT answer from the options given below:

• A. A, B, C, D
• B. D, B, C, A
• C. B, A, D, C
• D. C, B, D, A

Hint:

Memorize the coordination numbers for common crystal structures: Diamond (4), NaCl (6), BCC/CsCl (8), and HCP/FCC (12). This is a frequent topic in solid-state physics questions.

Answer 1

The Correct Option is A

Step 1: Determine the coordination number for each crystal structure. The coordination number is the number of nearest neighbors of an atom in the crystal lattice. - A. Diamond: In the diamond cubic structure, each carbon atom is tetrahedrally bonded to four other carbon atoms. The coordination number is 4. - B. Sodium Chloride (NaCl): In the rock salt structure, each ion (e.g., Na\(^+\)) is surrounded by six ions of the opposite charge (e.g., Cl\(^-\)) in an octahedral arrangement. The coordination number is 6. - C. Cesium Chloride (CsCl): In the CsCl structure, each ion is at the center of a cube of eight ions of the opposite charge. The coordination number is 8. - D. Zinc (HCP): Zinc has a Hexagonal Close-Packed (HCP) structure. In any close-packed structure (HCP or FCC), each atom is in contact with 12 other atoms (6 in its own plane, 3 above, and 3 below). The coordination number is 12.
Step 2: Arrange the structures in ascending order of their coordination number. The coordination numbers are: - Diamond (A): 4 - Sodium Chloride (B): 6 - Cesium Chloride (C): 8 - Zinc (HCP) (D): 12 Arranging these in ascending order gives the sequence: A (4)<B (6)<C (8)<D (12). The correct order is A, B, C, D.