Question

The atomic number of $V,Cr,Mn$ and $Fe$ are $23,24,25$ and $26$ respectively. Which one of these may be expected to have the highest second ionisation enthalpy?

• A. $V$
• B. $Cr$
• C. $Mn$
• D. $Fe$

Answer 1

The correct option is B $Cr$

The electronic configuration of the uni positive ions are given below:
$V^{+}=3d^{3}4s^1$
$C{r}^{+}=3d^5$
$M{n}^{+}=3d^{5}4s^1$
$F{e}^{+}=3d^{6}4s^1$

The $I{E}_2$ of $Cr$ will be the highest as $C{r}^{+}$ has a half-filled d-subshell.