Answer: AgCl with Ag+ in interstitial sites.
- A NaCl missing equal Na+ and Cl-
- B AgCl with Ag+ in interstitial sites
- C ZnO losing oxygen
- D FeO with Fe<sup>3+</sup> replacing Fe<sup>2+</sup>
Correct answer: B. AgCl with Ag+ in interstitial sites
Explanation: In AgCl, smaller Ag⁺ ions can shift to interstitial positions, creating a Frenkel defect without changing density.
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.