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

Which of the following has the highest electron affinity?

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

Electronic configurations of four elements $A, B, C$ and $D$ are given below :
$(A)$ $1s^2 2s^2 2p^6$
$(B)$ $1s^2 2s^2 2p^4$
$(C)$ $1s^2 2s^2 2p^6 3s^1$
$(D)$ $1s^2 2s^2 2p^5$
Which of the following is the correct order of increasing tendency to gain electron :

The formation of the oxide ion $O^{2-}_{(g)}$ requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^{-} \to O^{-}_{(g)}; \Delta H = -142 \, kJ \, mol^{-1}$
$O^{-}_{(g)} + e^{-} \to O^{2-}_{(g)}; \Delta H = 844 \, kJ \, mol^{-1}$
This is because:

Which of the following is correct for the electron affinity of halogens?