${\mathrm{EA}}_1$ of $\mathrm{Cu}$ is $-123 \mathrm{kJ} {\mathrm{mol}}^{-1}$ whereas ${\mathrm{EA}}_1$ of $\mathrm{Zn}$ is $+87 \mathrm{kJ} {\mathrm{mol}}^{-1}$. Explain:

Using the data given below, predict the nature of heat changes for the reaction. 

$\mathrm{Mg}\left(\mathrm{g}\right)+2\mathrm{F}\left(\mathrm{g}\right)⟶{\mathrm{Mg}}^{2+}\left(\mathrm{g}\right)+2{\mathrm{F}}^{-}\left(\mathrm{g}\right)$

${\mathrm{IE}}_1$ and ${\mathrm{IE}}_2$ of $\mathrm{Mg}\left(\mathrm{g}\right)$ are$737.7$ and $1451 \mathrm{kJ} {\mathrm{mol}}^{-1}$. ${\mathrm{EA}}_1$ for $\mathrm{F}\left(\mathrm{g}\right)$ is $-328 \mathrm{kJ} {\mathrm{mol}}^{-1}$.

Which of the following pairs of elements would have a more negative electron gain enthalpy? Explain:

$\mathrm{N}$ or $\mathrm{O}$.