Answer: 4.
- A 1
- B 2
- C 4
- D 8
Correct answer: C. 4
Explanation: FCC Cl⁻: 4 Cl⁻ per unit cell. All octahedral holes occupied by Na⁺: 4 Na⁺ per unit cell. Therefore 4 formula units of NaCl per unit cell.
The three cubic unit cells: Simple Cubic has atoms only at corners; Body-Centred adds one atom at the centre; Face-Centred adds one atom at the centre of each of the 6 faces, giving the highest packing efficiency.
Concept context
Explore the ordered world of crystalline solids: unit cells, packing, defects, and how structure determines electrical and magnetic properties.