Answer: Delocalised pi electrons in the layers are free to move.
- A Delocalised pi electrons in the layers are free to move
- B It is held together largely by metallic bonding like a true metal
- C It contains ionic bonds that allow charge carriers to migrate
- D Most of its valence electrons are fixed within localised sigma bonds
Correct answer: A. Delocalised pi electrons in the layers are free to move
Explanation: In graphite, each C is sp<sup>2</sup> hybridised; the unhybridised p electrons form delocalised pi bonds along the layers, enabling electrical conductivity.
Diamond's rigid 3D tetrahedral network makes it the hardest natural material, while graphite's flat hexagonal sheets are held together only by weak forces, letting them slide past each other (used as a lubricant and in pencils).
Concept context
Covers the Boron family (Group 13: B, Al) and the Carbon family (Group 14: C, Si, Ge, Sn, Pb). Key topics include Lewis acid behaviour of BF₃, borax bead test, silicates, silicones, allotropes of carbon, and trends in properties down the group.