Which of the following ions is colourless in solution?

Which elements of the $3d$ series do not show variable valency?

State whether the following statements are true or false:
$(i)$ Atomic size increases with an increase in the atomic number of elements.
$(ii)$ The electron gain enthalpy for noble gases is approximately zero.
$(iii)$ The first element of the actinoid series is $Th$ and the last element is $Lu$.
$(iv)$ The general electronic configuration of $d$-orbitals is always $(n-1)d^{1-10}ns^2$.

Which of the following metal ions has the maximum number of unpaired electrons?

The electrode potential of $M^{2+} / M$ for $3d$-series elements shows a positive value for which of the following?

Consider the hydrated ions of $Ti^{2+}$,$V^{2+}$,$Ti^{3+}$,and $Sc^{3+}$. The correct order of their spin-only magnetic moments is