Why are zero group elements called noble gases or inert gases?

Select in each pair, the one having lower ionization energy and explain the reason.

$\mathrm{I}$ and ${\mathrm{I}}^{-}$.

Select in each pair, the one having lower ionization energy and explain the reason.

$\mathrm{Br}$ and $\mathrm{K}$.

Select in the given pair, the one having lower ionization energy and explain the reason.

$\mathrm{Li}$ and ${\mathrm{Li}}^{+}$.

Select in each pair, the one having lower ionization energy and explain the reason.

$\mathrm{Ba}$ and $\mathrm{Sr}$.

Select in each pair, the one having lower ionization energy and explain the reason.

$\mathrm{O}$ and $\mathrm{S}$.

Select in the given pair, the one having lower ionization energy and explain the reason.

$\mathrm{Be}$ and $\mathrm{B}$.

Select in the given pair, the one having lower ionization energy and explain the reason: $\mathrm{N}$ and $\mathrm{O}$.