Answer: Zinc ions and electrons are released; Zn 2+ occupy interstitial sites (metal excess defect).
- A It largely decomposes on heating into separate Zn metal and O<sub>2</sub> gas as frequently observed in practice
- B Zinc ions and electrons are released; Zn<sup>2+</sup> occupy interstitial sites (metal excess defect)
- C It absorbs extra atmospheric oxygen into its crystal lattice on heating in many documented cases
- D It converts into the higher oxide ZnO2 upon gentle heating according to conventional understanding
Correct answer: B. Zinc ions and electrons are released; Zn<sup>2+</sup> occupy interstitial sites (metal excess defect)
Explanation: Heating ZnO causes it to lose some O₂; excess Zn²⁺ occupy interstitial sites with trapped electrons, creating a metal-excess defect and yellow colour (trapped electrons absorb blue light).
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.