Answer: Graphite (covalent).
- A NaCl (ionic)
- B SiO<sub>2</sub> (covalent)
- C Ice (molecular)
- D Graphite (covalent)
Correct answer: D. Graphite (covalent)
Explanation: Graphite has delocalised pi electrons that can move through the layers, making it an electrical conductor unlike most covalent solids.
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.