Answer: Monoxide, peroxide and superoxide.
- A Peroxide, superoxide and monoxide
- B Superoxide, monoxide and peroxide
- C Monoxide, peroxide and superoxide
- D Monoxide, superoxide and peroxide
Correct answer: C. Monoxide, peroxide and superoxide
Explanation: Lithium forms mainly the monoxide Li<sub>2</sub>O, sodium forms the peroxide Na<sub>2</sub>O<sub>2</sub>, and potassium (and heavier metals) form superoxides such as KO<sub>2</sub>.
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.