What is the correct order of electron affinity for the elements of the oxygen group in the periodic table?

What is electron gain enthalpy $\left( \Delta_{eg} H \right)$? When does its value become positive and negative?

The electron affinity values of elements $A, B, C$ and $D$ are respectively $-135, -60, -200$ and $-348 \ kJ \ mol^{-1}$. The outer electronic configuration of element $B$ is

The second electron gain enthalpy of an element:

To which of the following atoms is the attachment of an electron most difficult?

Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.