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

Match the following metal ions with their respective colours:

Metal ion	Colour
$A. V^{4+}$	$I. Colourless$
$B. Ti^{3+}$	$II. Purple$
$C. Ti^{4+}$	$III. Green$
$D. Ni^{2+}$	$IV. Blue$
	$V. Yellow$

Among $Sc$,$Mn$,$Co$ and $Cu$,identify the element with the highest enthalpy of atomisation. The spin-only magnetic moment value of that element in its $+2$ oxidation state is $......... \text{BM}$ (in nearest integer).

Transition metals are not characterized by

The correct order of density for the $3d$ series elements is:

The colour of an electrolyte solution depends on