Answer: 6.
- A 4
- B 6
- C 8
- D 12
Correct answer: B. 6
Explanation: In the NaCl structure, each Na⁺ is surrounded by 6 Cl⁻ and each Cl⁻ by 6 Na⁺; coordination number is 6.
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.