Answer: Very small size and high charge density (diagonal relationship with Mg).
- A Very small size and high charge density (diagonal relationship with Mg)
- B Its position as the most chemically reactive metal in Group 1
- C Its unusually low electronegativity compared to the rest of Group 1
- D Its status as the heaviest element within Group 1
Correct answer: A. Very small size and high charge density (diagonal relationship with Mg)
Explanation: Li is anomalously small and has a high charge density, causing it to behave more like Mg in many properties (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.