Which one of the following lanthanide ions does not exhibit paramagnetism?

If the ionic radius of $_{57}La^{3+}$ is $1.06 \ \mathring{A}$,then the ionic radius of $_{71}Lu^{3+}$ will be approximately close to which of the following values in $\mathring{A}$?

$4f^2$ electronic configuration is found in

Which pair of ions among the following can be separated by the precipitation method?

The common stable oxidation states of $Eu$ and $Gd$ are respectively

Name the members of the lanthanoid series which exhibit $+4$ oxidation state and those which exhibit $+2$ oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.