Question

why lithium only forms normal oxide , sodium forms peroxides and other metal forms superoxides?????

Answer 1

The atomic size of lithium is very small therefore it can form bond with one oxygen atom...as the size of atom increases,its holding capacity also increases...therefore sodium can form peroxide besides oxide and pottasium forms  superoxides besides oxide and peroxides
Hope it helps.....

Answer 2

The atomic size of lithium is very small therefore it can form bond with one oxygen atom.As the size of atoms increases,it holding capacity also increases.
Therefore sodium can form peroxide besides oxide and pottasium forms superoxides besides oxide and peroxide...