The formation of the oxide ion, O2-(g), from oxygen atom requires first an exothermic and then an endothermic step as shown below: O ( g )+ e - longrightarrow O ( g )-;Δ f H °=-141 kJ mol -1 O ( g )+ e - longrightarrow O ( g )2- ; Δ f H °=+780 kJ mol -1 Thus process of formation of O2- in gas phase is unfavourable even thought O2- is isoelectronic with neon. It is due to the fact that,

Question

The formation of the oxide ion, O2-(g), from oxygen atom requires first an exothermic and then an endothermic step as shown below: O ( g )+ e - longrightarrow O ( g )-;Δ f H °=-141 kJ mol -1 O ( g )+ e - longrightarrow O ( g )2- ; Δ f H °=+780 kJ mol -1 Thus process of formation of O2- in gas phase is unfavourable even thought O2- is isoelectronic with neon. It is due to the fact that, (A) Oxygen is more electronegative (B) Addition of electron in oxygen results in larger size of the ion (C) Electron repulsion outweighs the stability gained by achieving noble gas configuration (D) O- ion has comparatively smaller size than oxygen atom

Tardigrade Admin · Accepted Answer

Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, formation of O2- in gas phase is unfavourable.

Oxygen is more electronegative

Addition of electron in oxygen results in larger size of the ion

Electron repulsion outweighs the stability gained by achieving noble gas configuration

$O^{-}$ ion has comparatively smaller size than oxygen atom

Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, formation of $O^{2 -}$ in gas phase is unfavourable.

Oxygen is more electronegative

Addition of electron in oxygen results in larger size of the ion

Electron repulsion outweighs the stability gained by achieving noble gas configuration

O− ion has comparatively smaller size than oxygen atom

Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, formation of O2− in gas phase is unfavourable.

$O^{-}$ ion has comparatively smaller size than oxygen atom

Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, formation of $O^{2 -}$ in gas phase is unfavourable.