The formation of the oxide ion, , from a gaseous oxygen atom requires first an exothermic and then an endothermic step. The second electron gain enthalpy is positive primarily because:

Question

The formation of the oxide ion, $O^{2-}_{(g)}$, from a gaseous oxygen atom requires first an exothermic and then an endothermic step. The second electron gain enthalpy is positive primarily because:

Prashant Kotian · Accepted Answer

Correct answer: C. The first electron addition is exothermic (). Adding a second electron means forcing a negative electron onto an already negatively charged ion (). The strong inter-electronic Coulombic repulsion overwhelmingly outweighs the nuclear attraction, making the process highly endothermic ().

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