Published by:
CGP EDU Academic Team
Published on: August 14, 2026
The formation of the oxide ion, O 2– (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e – 
O – (g) ; Δ eg H = – 141 kJmol –1 O
– (g) + e – 
O 2– (g) ; Δ eg H = + 780 kJmol –1 Thus process of formation of O
2– in gas phase is unfavourable even though O 2– is isoelectronic with neon. It is due to the fact that:
Text Solution
Verified by ExpertsThe correct answer is:
C
There is electrostatic repulsion between the two species having same type of charge. So energy has to be given for the addition of additional electron to O – .
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