Electron gain enthalpy of noble gases is positive. Explain.

In the following pair, state which atom/ion has higher ionisation enthalpy and more negative electron gain enthalpy?
$\mathrm{I}, {\mathrm{I}}^{-}$

In the following pair, state which atom/ion has higher ionisation enthalpy and more negative electron gain enthalpy.

$\mathrm{Br}, {\mathrm{Br}}^{-}$.

In the following pair, state which atom/ion has higher ionisation enthalpy and more negative electron gain enthalpy? 

$\mathrm{Li}, {\mathrm{Li}}^{+}$

In the following pair, state which atom/ion has higher ionisation enthalpy and more negative electron gain enthalpy?

 $\mathrm{Br}, \mathrm{I}$