Answer
a) $Sc^{3+}$
b) $Te^{2-}$
c) $Ce^{4+}$ and $Ti^{4+}$
d) $Ba^{2+}$
Work Step by Step
The ions that have noble gas electron configurations are those that have a completely filled valence electron shell, similar to the stable electron configuration of a noble gas.
In option (a), the ion $Sc^{3+}$ has the configuration of $Ar$.
In option (b), the ion $Te^{2-}$ has the configuration of $Xe$.
In option (c), the ion $Ce^{4+}$ has the configuration of $Xe$ and $Ti^{4+}$ has the configuration of $Ar$.
In option (d), the ion $Ba^{2+}$ has the configuration of $Xe$.
