Question

Explain why lithium on being heated in air forms the monoxide but not peroxide

Answer 1

Lithium forms an oxide i.e. Li20 not monoxide but when heated violently it forms Lithium peroxide (Li2O2).

Answer 2

Lithium cannot form peroxide while sodium can because positive charge is located over small size of lithium and hence there is positive field around it which will attract negative ion so strongly that it will not permit oxide ion to combine with another oxide ion

Hence lithium forms monoxide while in case of sodium charge is located over comparatively bigger atom which allows oxide ion to combine with another oxide ion hence.. Peroxide is formed

While in other case superoxide is formed due to combination. Of two peroxide ions.