Which one of the alkali metals forms only the normal oxide, ${\text{M}}_2\text{O}$ on heating in air?

Alkali metals react differently with oxygen based on their size:Lithium ($\text{Li}$): Forms mainly the normal oxide (${\text{Li}}_2\text{O}$).Sodium ($\text{Na}$): Forms the peroxide (${\text{Na}}_2{\text{O}}_2$) as the major product.Potassium ($\text{K}$), Rubidium ($\text{Rb}$), Caesium ($\text{Cs}$): Form superoxides (${\text{MO}}_2$).The small size of ${\text{Li}}^{+}$ stabilizes the small ${\text{O}}^{2-}$ ion but cannot stabilize larger ions like ${\text{O}}_2^{2-}$ or ${\text{O}}_2^{-}$.