Answer: NaCl has ions of similar size and high coordination number so ions cannot easily fit into interstitial positions.
- A NaCl has ions of similar size and high coordination number so ions cannot easily fit into interstitial positions
- B NaCl's sodium cation and chloride anion are said to differ very greatly in their respective ionic radii as frequently observed in practice
- C NaCl is described as a predominantly covalent compound rather than as a genuinely ionic compound in many documented cases
- D NaCl generally happens to have an unusually low melting point when compared with most other ionic salts according to conventional understanding
Correct answer: A. NaCl has ions of similar size and high coordination number so ions cannot easily fit into interstitial positions
Explanation: Frenkel defects require one ion to move into a smaller interstitial site. In NaCl, both Na⁺ and Cl⁻ are too large to fit into interstitial sites without too much lattice distortion; hence Schottky defects are preferred.
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.