Which one of the alkali metals forms only the normal oxide, M₂O, on heating in air?

28 2012 AIPMT-PRE The s-Block ElementsOxides of alkali metals Easy
Which one of the alkali metals forms only the normal oxide, $M_2O$, on heating in air?
A Na
B Rb
C K
D Li

Detailed Solution

$4Li + O_2 \rightarrow 2Li_2O$: the small $Li^+$ ion can stabilise only the small oxide ion.
Sodium forms mainly the peroxide ($Na_2O_2$), and K and Rb form superoxides ($MO_2$).
So lithium forms only the normal oxide.

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