Answer
a) $Mg^{2+}$
b) $Be^{2+}$
c) $Fe^{3+}$
d) $F^-$
e) $Cl-$
f) $SO_4^{2-}$
Work Step by Step
a) $Mg^{2+}$ is more strongly hydrated than $Na^+$ because they are roughly the same size, but $Mg^{2+}$ has a greater charge.
b) $Be^{2+}$ is more strongly hydrated than $Mg^{2+}$ because they have the same charge, but $Be^{2+}$ is smaller.
c) $Fe^{3+}$ is more strongly hydrated than $Fe^{2+}$ because they are roughly the same size, but $Fe^{3+}$ has a greater charge.
d) $F^-$ is more strongly hydrated than $Br^-$ because they have the same charge, but $F^-$ is smaller.
e) $Cl-$ is more strongly hydrated than $ClO_4^-$ because they have the same charge, but $Cl^-$ is smaller.
f) $SO_4^{2-}$ is more strongly hydrated than $ClO_4^-$ because they are roughly the same size, but $SO_4^{2-}$ has a greater charge.
