STANDARD Chemistry Electron Affinity MCQ Question
The formation of the oxide ion O₂⁻(g) requires first an exothermic and then an endothermic step as shown below O(g) + e⁻ = O⁻(g) ΔH° = -142 kJ mol⁻¹ O⁻(g) + e⁻ = O₂⁻(g) ΔH° = 844 kJ mol⁻¹ This is because
O⁻ ion will tend to resist the addition of another electron
Oxygen has high electron affinity
Oxygen is more electronegative
O⁻ ion has comparatively larger size than oxygen atom
Correct Answer
Detailed Explanation
The addition of a second electron to an atom or ion is always endothermic due to electron-electron repulsion.
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