Answer: Pb > Sn > Ge.
- A Ge > Sn > Pb
- B Pb > Sn > Ge
- C Sn > Pb > Ge
- D Ge > Pb > Sn
Correct answer: B. Pb > Sn > Ge
Explanation: The inert-pair effect strengthens down the group, so the +2 state is most stable for lead: Pb > Sn > Ge.
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.