Q. The formation of the oxide ion $O^{2 -}(g)$ requires first an exothermic and then an endothermic step as shown below $O(g) + e^{-} = O^{-}(g);\ \ \mathrm{\Delta}H^{o} = - 142\ kJ\ mol^{- 1}$ $O^{-}(g) + e^{-} = O^{2 -}(g),\ \mathrm{\Delta}H^{o} = 844\ kJ\ mol^{- 1}$ This is because
A) $O^{-}$ ion will tend to resist the addition of another electron
B) Oxygen has high electro affinity
C) Oxygen is more electronegative
D) $O^{-}$ ion has comparatively larger size than oxygen atom
Explanation
(a)
The addition of second electron in an atom or ion is always endothermic as the incoming electron experience the greater force of repulsion
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.