Answer: Magnesium (Mg).
- A Magnesium (Mg)
- B Calcium (Ca)
- C Beryllium (Be)
- D Barium (Ba)
Correct answer: A. Magnesium (Mg)
Explanation: Magnesium is very light (density 1.74 g/cm<sup>3</sup>) and is alloyed with aluminium to make lightweight, strong alloys for aerospace.
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.