Question:
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:
Correct Option: , 4
Solution:
(A) $2 \mathrm{Mg}+\mathrm{O}_{2} \rightarrow 2 \mathrm{MgO}$ (Diamagnetic)
(B) $2 \mathrm{Na}+\mathrm{O}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{O}$ (Diamagnetic)
$2 \mathrm{Na}+\underset{\text { (excess) }}{\mathrm{O}_{2}} \rightarrow \mathrm{Na}_{2} \mathrm{O}_{2}$ (Diamagnetic)
(C) $2 \mathrm{Ca}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CaO}$ (Diamagnetic)
$\mathrm{Ca}+\mathrm{O}_{2} \rightarrow \mathrm{CaO}_{2}$ (Diamagnetic)
(D) $\mathrm{K}+\underset{(\text { exess })}{\mathrm{O}_{2}} \rightarrow \mathrm{KO}_{2}$ (Paramagnetic)