Answer: melts in the warmth of a hand.
- A is a gas at room temperature
- B melts in the warmth of a hand
- C is quite strongly radioactive
- D is clearly ferromagnetic
Correct answer: B. melts in the warmth of a hand
Explanation: Gallium melts at about 30 °C, so it will liquefy in the warmth of a hand.
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.