When heated in air,the alkali metals form various oxides. Mention the oxides formed by $Li$,$Na$ and $K$.

(N/A) Alkali metals react with $O_{2}$ and their reactivity increases down the group. These elements form three types of oxides: normal oxides,peroxides,and superoxides.
$1. \ Li$ forms mainly the normal oxide: $4 Li + O_{2} \xrightarrow{\Delta} 2 Li_{2}O$
$2. \ Na$ forms mainly the peroxide: $2 Na + O_{2} \xrightarrow{\Delta} Na_{2}O_{2}$
$3. \ K$ forms mainly the superoxide: $K + O_{2} \xrightarrow{\Delta} KO_{2}$
Superoxide $(O_{2}^{-})$ is stable only with large-sized cations like $K^{+}$,$Rb^{+}$,and $Cs^{+}$.