Select the substance(s) which is/are used to convert ${\mathrm{Mn}}^{2+}$ to ${\mathrm{MnO}}_4^{-}$.

Assign reason for the following:

${\mathrm{Ce}}^{3+}$ can be easily oxidised to ${\mathrm{Ce}}^{4+}.$

Assign reason for the following:

$\mathrm{Lu}(\mathrm{OH}{)}_3$ is a weaker base than $\mathrm{La}(\mathrm{OH}{)}_3.$

Explain:

why are ${\mathrm{Sm}}^{2+}, {\mathrm{Eu}}^{2+}$ and ${\mathrm{Yb}}^{2+}$ good reducing agent?

Explain:

can Lanthanum $(\mathrm{Z}=57)$ exhibit $+4$ oxidation state?

Explain:

why is $+3$ oxidation state of gadolinium $(\mathrm{Z}=64)$ and lutetium $(\mathrm{Z}=91)$ especially stable?

Explain:

Why do $\mathrm{Zr}$ and $\mathrm{Hf}$ exhibit similar properties?

The outer electronic configuration of two members of the lanthanide series are as follows:

$4{\mathrm{f}}^{1}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$ and $4{\mathrm{f}}^{7}5{\mathrm{d}}^{0}6{\mathrm{s}}^2$.

What are their atomic numbers? Predict the oxidation states exhibited by these elements in their compounds.