Answer: 0.414.
- A 0.155
- B 0.225
- C 0.414
- D 0.732
Correct answer: C. 0.414
Explanation: For a cation to fit into an octahedral hole touching all 6 surrounding anions: r(cation)/r(anion) must be at least 0.414 (the critical radius ratio for 6-coordination).
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.