Answer: A 2 B 3.
- A A<sub>2</sub>B<sub>3</sub>
- B A<sub>3</sub>B<sub>2</sub>
- C AB<sub>2</sub>
- D A<sub>2</sub>B
Correct answer: A. A<sub>2</sub>B<sub>3</sub>
Explanation: For N anions there are N octahedral voids; two-thirds filled gives 2N/3 cations, so A:B = 2N/3 : N = 2:3, i.e. A<sub>2</sub>B<sub>3</sub>.
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.