Answer: 12 and 26%.
- A 12 and 26%
- B 8 and 32%
- C 6 and 48%
- D 12 and 36%
Correct answer: A. 12 and 26%
Explanation: HCP has the same coordination number (12) and packing efficiency (74%) as FCC, leaving a void fraction of 1 - 0.74 = 0.26, or 26%.
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.