Which among the following elements has a completely filled $4d$ orbital?

The set having ions which are coloured and paramagnetic both is :

Which of the following graphs is the correct representation of the relationship between atomic number $(Z)$ and the magnetic moment of $d-$block elements? [Outer electronic configuration : $(n - 1)d^x\ ns^{1\ or\ 2}$]

Which element from the following does $NOT$ exhibit a spin-only magnetic moment in the $+3$ oxidation state?

Why is the $E^{\Theta }$ value for the $Mn^{3+}/Mn^{2+}$ couple much more positive than that for $Cr^{3+}/Cr^{2+}$ or $Fe^{3+}/Fe^{2+}$? Explain.

$A$ substance which is not paramagnetic is