The combustion of Li, Na, K in excess of air gives major oxides

Explanation

`Li^(+)` is very small in size and has strong field around it. It can stabilize only small sized oxide `O^(2-)`ion and therefore, forms only `Li_2O`. It cannot stabilize other large anions such as peroxide `(O_2^(2-))` and superoxide `(O_(2)^(-))`.
`Na^(+)` being larger in size can stabilize large peroxide ion `(O_(2)^(2-))` and therefore, forms peroxides.
`K^(+)` being large can also stabilize large superoxide ion `(O_(2)^(-))` forming superoxides.