Which of the following ions is colourless in spite of the presence of unpaired electrons?

Match the elements in List-$I$ with their electronic configurations in List-$II$.

List-$I$	List-$II$
$(1)$ $Ti^+$	$(A)$ $(n-1)d^4ns^2$
$(2)$ $_{30}Zn$	$(B)$ $(n-1)d^{10}ns^1$
$(3)$ $_{24}Cr$	$(C)$ $(n-1)d^2ns^0$
$(4)$ $_{29}Cu$	$(D)$ $(n-1)d^5ns^1$
	$(E)$ $(n-1)d^0ns^2$
	$(F)$ $(n-1)d^{10}ns^2$

$A$ first row transition metal in its $+2$ oxidation state has a spin-only magnetic moment value of $3.86 \ BM$. The atomic number of the metal is

Which of the following statements are correct about $Zn, Cd$ and $Hg$?
$A$. They exhibit high enthalpy of atomization as the d-subshell is full.
$B$. $Zn$ and $Cd$ do not show variable oxidation state while $Hg$ shows $+I$ and $+II$.
$C$. Compounds of $Zn, Cd$ and $Hg$ are paramagnetic in nature.
$D$. $Zn, Cd$ and $Hg$ are called soft metals.
Choose the most appropriate from the options given below:

The catalytic activity of transition elements is related to their

Which of the following elements are included in the fourth transition series?