Question

Four successive members of the first-row transition elements are listed below with atomic numbers. From the elements listed below, which one is expected to have the highest $E_{M^{3+}/M^{2+}}^0$ value?

• A. $Cr(Z=24)$
• B. $Mn(Z=25)$
• C. $Fe(Z=26)$
• D. $Co(Z=27)$

Answer 1

The correct option is D $Co(Z=27)$

$\begin{array}{c}I\cdot E=13.6z^2(\frac{1}{n_1^2}-\frac{1}{n_2^2})\\ \text{Ionisation}\text{energy}\to IE\\ \text{atomic number}\to z\\ \therefore I\cdot E\propto z^2\end{array}$

$\therefore Co(z=27)\text{has highest I.E.}$