Answer: Both form nitrides with N 2 and carbonates that decompose on heating.
- A Both form highly soluble carbonates
- B Both form nitrides with N<sub>2</sub> and carbonates that decompose on heating
- C Both form stable solid hydrogencarbonates
- D Both impart a characteristic crimson colour to the Bunsen flame
Correct answer: B. Both form nitrides with N<sub>2</sub> and carbonates that decompose on heating
Explanation: Li resembles Mg: both react with N<sub>2</sub> to form nitrides, their carbonates decompose on heating, and their hydrogencarbonates do not exist as solids, reflecting the diagonal relationship.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.