Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.
Or
What are successive electron gain enthalpies? Explain why second or higher electron gain enthalpy will have positive value.

When a single electron is added to a gaseous atom, it forms a monovalent anion and the enthalpy released is called the first electron gain enthalpy. However, when we add the second electron to the negatively charged ion, this addition of electron will be strongly opposed due to the coulomb forces of repulsion. Hence enthalpy must be supplied for the addition of the second electron. For these reasons, the value of second electron affinity or higher electron affinity will have a positive value. For example

First electron gain enthalpy:



Second electron gain enthalpy: