The process requiring absorption of energy is

Consider the following conversions:
$(i) \, O_{(g)} + e^- \to O_{(g)}^{-}, \Delta H_1$
$(ii) \, F_{(g)} + e^- \to F_{(g)}^{-}, \Delta H_2$
$(iii) \, Cl_{(g)} + e^- \to Cl_{(g)}^{-}, \Delta H_3$
$(iv) \, O_{(g)}^{-} + e^- \to O_{(g)}^{2-}, \Delta H_4$
Based on the given information,which statement is incorrect?

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

What is electron affinity?

The correct order of increasing electron affinity of the following elements is

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