Magnesium does not impart characteristic colour to the bunsen-burner flame. — s Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: When alkali metals are heated in excess oxygen, they form different oxides based on the size of their cations. Small Li+ forms oxide (Li2O); Na+ forms peroxide (Na2O2). Step 2: Larger alkali metal cations like K+, Rb+, and Cs+ have low charge densities and are stabilized by large, low charge-density anions like the superoxide ion (O2^-). Step 3: Therefore, potassium burns in oxygen to yield potassium superoxide (KO2), making option (b) the correct choice.