Q. The correct order of $E{^\circ}_{M^{2 +}/M}$ values with negative sign for the four successive elements Cr, Mn, Fe and Co is
A) $Mn\ > Cr\ > Fe\ > Co$
B) $Cr\ > Fe\ > Mn\ > Co$
C) $Fe\ > Mn\ > Cr\ > Co$
D) $Cr\ > Mn\ > Fe\ > Co$
Explanation
(a)
Usually across the first transition series, the negative values for standard electrode potential decrease except for Mn due to stable $d^{5}$ –configuration.
So, correct order : $Mn\ > Cr\ > Fe\ > Co$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.