Answer: Si > Ge > Sn > Pb.
- A Pb > Sn > Ge > Si
- B Si > Ge > Sn > Pb
- C Ge > Si > Pb > Sn
- D Sn > Pb > Si > Ge
Correct answer: B. Si > Ge > Sn > Pb
Explanation: The +4 state becomes less stable down the group as the inert-pair effect strengthens, so stability of +4 runs Si > Ge > Sn > Pb.
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.