Identify the outer electronic configuration of the $first$ element of the $first$ transition series.

Which of the following represents the decreasing order of the second ionization enthalpy $(I.P_2)$?

Although $Zr$ belongs to the $4d$ transition series and $Hf$ belongs to the $5d$ transition series,it is quite difficult to separate them. Why?

What is the total number of transition series of $d$-block elements?

For $M^{2+} / M$ and $M^{3+} / M^{2+}$ systems,the ${E^{\Theta}}$ values for some metals are as follows:
$Cr^{2+} / Cr : -0.9 \ V$
$Cr^{3+} / Cr^{2+} : -0.4 \ V$
$Mn^{2+} / Mn : -1.2 \ V$
$Mn^{3+} / Mn^{2+} : +1.5 \ V$
$Fe^{2+} / Fe : -0.4 \ V$
$Fe^{3+} / Fe^{2+} : +0.8 \ V$
Use this data to comment upon:
$(i)$ The stability of $Fe^{3+}$ in acid solution as compared to that of $Cr^{3+}$ or $Mn^{3+}$ and
$(ii)$ The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

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