Answer: increases.
- A decreases
- B increases
- C remains constant
- D drops to zero
Correct answer: B. increases
Explanation: Because of the inert-pair effect, the +2 state becomes more stable down the group (Pb²⁺ is more stable than Pb⁴⁺).
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.