The formation of the oxide ion requires first an exothermic and then an endothermic step as shown below.
This is because
oxygen is more electronegative
oxygen has high electron affinity
ion will tend to resist the addition of another electron
ion has comparatively larger size than oxygen atom
As we learnt in
Successive Ionization enthalpies -
The ionisation enthalpies to remove first, second, third etc.Electrons from an isolated gaseous atom are called successive ionisation enthalpies.
- wherein
As we observed before, successive ionization energies are higher. Similarly, successive electron gain enthalpies are higher.
That is because it is harder to gain another electron in which is already negatively charged.
Option 1)
oxygen is more electronegative
This option is incorrect.
Option 2)
oxygen has high electron affinity
This option is incorrect.
Option 3)
ion will tend to resist the addition of another electron
This option is correct.
Option 4)
ion has comparatively larger size than oxygen atom
This option is incorrect.
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