• # question_answer 67)   When heated in air, the alkali metals form various oxide. Mention the oxides formed by Li, Na and K.

The effect of atmosphere increases from Li to Cs. Affinity towards oxygen of alkali metals is high and increases from Li to Cs. On heating, lithium forms monoxide, $L{{i}_{2}}O;$ sodium forms the peroxide, $N{{a}_{2}}{{O}_{2}}$ and potassium superoxide$K{{O}_{2}}$. $4Li+{{O}_{2}}\to 2L{{i}_{2}}O(Lithium\,oxide)$ $4Na+{{O}_{2}}\to \underset{SOdium\,oxide}{\mathop{2N{{a}_{2}}O}}\,\xrightarrow{{{O}_{2}}}\underset{Sodium\,peroxide}{\mathop{N{{a}_{2}}{{O}_{2}}}}\,$ $4K+{{O}_{2}}\to 2{{K}_{2}}O\xrightarrow{{{O}_{2}}}{{K}_{2}}{{O}_{2}}\xrightarrow{{{O}_{2}}}\underset{\begin{smallmatrix} Potassium \\ \text{superoxide} \end{smallmatrix}}{\mathop{{{K}_{2}}{{O}_{2}}}}\,$