Which of the following metal ions is colourless?

The $E^{\Theta} (M^{2+} / M)$ value for copper is positive $(+0.34 \ V)$. What is the possible reason for this? (Hint: consider its high $\Delta_{a} H^{\Theta}$ and low $\Delta_{hyd} H^{\Theta}$)

Which of the following forms a colourless solution in aqueous medium?

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ The magnetic moment arises from the spin and orbital motion of electrons.
$(b)$ The magnetic moment of $Mn^{2+}$ is $5.92 \ BM$.
$(c)$ Interstitial compounds are covalent compounds.

Name the periodic element,which does not show variable oxidation states.

Gadolinium has a low value of third ionisation enthalpy because of $......$