Which one of the following ions is colourless?

Which of the following sets of elements does not possess $f$-electrons?

The second ionisation energy of the following elements follows the order

Which of the following elements in their respective oxidation states does not develop spin only magnetic moment? $[Ti (Z=22), Zn(Z=30), V(Z=23), Cu(Z=29)]$

The correct decreasing order of spin only magnetic moment values $(BM)$ of $Cu^{+}$,$Cu^{2+}$,$Cr^{2+}$ and $Cr^{3+}$ ions is $:$

Which of the following groups of transition metals is known as coinage metals?