Would you expect the second electron gain enthalpy of O. as positive, more negative or less. negative than the first ? Justify your answer.

Explanation

Second electron gain enthalpy of O is positive because after the gain of one electron the oxygen atom acquires negative charge. Now when the second electron approaches the negatively charged oxygen atom, there is negative - negative repulsion. Hence, energy is to be supplied, so second electron gain enthalpy becomes positive.