Knowing the electron gain enthalpy. values for O → O– and O → O2- as -141 and 702 kJ mol-1 respectively, how can you account for the formation of a large number of oxides having O2- species and not O–?(Hint: Consider lattice energy factor in the formation of compounds).

Knowing the electron gain enthalpy. values for O → O– and O → O

1.	Knowing the electron gain enthalpy. values for O → O– and O → O2- as -141 and 702 kJ mol-1 respectively, how can you account for the formation of a large number of oxides having O2- species and not O–?(Hint: Consider lattice energy factor in the formation of compounds).
Answer» Stability of an ionic compound depends on its lattice energy. More the lattice energy of a compound, more stable it will be Lattice energy is directly proportional to the charge carried by an ion. When a metal combines with oxygen, the lattice energy of the oxide involving O^2- ion is much more than the oxide involving O^- ion. Hence, we can say that formation of O^2- is energetically more favourable than formation of O^-.