Coinage metals are present in

Fill in the blanks:
$(a)$ The shielding effect of $d$-electrons is ......... effective than $p$-electrons.
$(b)$ $A$ decrease in exchange energy leads to a ......... in stability.
$(c)$ The maximum oxidation state of $Mn$ is ..........
$(d)$ The stability of $Mo(VI)$ and $W(VI)$ is found to be .......... than that of $Cr(VI)$.

Which of the following species is expected to show the highest magnetic moment? (At. Nos.: $Cr = 24$,$Mn = 25$,$Co = 27$,$Ni = 28$,$Cu = 29$)

Pair of transition metal ions having the same number of unpaired electrons is $:$

Which one of the following is an example of non-$typical$ transition elements?

The electronic configuration of gadolinium (atomic no. $64$) is