A s-block element (M) reacts with oxygen to form an oxide of the formula \(\mathrm{MO_2}\). The oxide is pale yellow in colour and paramagnetic. The element (M) is :
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- Mg
- Na
- Ca
- K
The Correct Option is D
Solution and Explanation
The larger alkali metals (K, Rb, Cs) form stable superoxides on burning in excess oxygen: \(\mathrm{K + O_2 \rightarrow KO_2}\), a yellow paramagnetic solid.
Na gives mainly \(\mathrm{Na_2O_2}\) (diamagnetic peroxide); Mg and Ca give normal oxides MgO and CaO.
Answer: (4) K
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