Question

Why first electron gain enthalpy of oxygen is negative and second electron gain enthalpy of oxygen is positive?

Answer 1

here is ur answer.....
When an electron is added to an isolated oxygenatom, it becomes uninegative ion. ... Hence more energy has to be supplied for the addition of an electron to this uninegative ion. Therefore , the second electron gain enthalpy is positivefor oxygen.


i hope it helps u......

and merry christmas

Answer 2

The elctronic configuration of oxygen is-

1s²2s²2$p^{4}$

So the p-orbital is close to half fill state, and as we know half filled and full filled orbital are more stable (due to minimum spin concept)...

so the Oxygen Atom doesnot allow to accept electron, and hence, 1st electron gain enthalpy of oxygen is negative.

For the 2nd time, Oxygen Atom needs only one electron in order to reach full fill state. So Oxygen Atom easily accepts one electron in orger to get stabilized...

That's why, second electron gain enthalpy of oxygen is positive....

Hope this helps...