Question

The transition metal ion with the highest magnetic moment is ________.

• A. $Fe^{2+}$
• B. $Mn^{2+}$
• C. $Ni^{2+}$
• D. $Co^{2+}$
• E. $Cr^{2+}$

Hint:

$d^5$ configuration in transition metals usually results in the highest spin-only magnetic moment.

Answer 1

The Correct Option is B

Step 1: Concept
Magnetic moment ($\mu$) is directly proportional to the number of unpaired electrons ($n$): $\mu = \sqrt{n(n+2)}$.

Step 2: Meaning
Determine the $d$-electron configuration for each ion.

Step 3: Analysis
$Mn^{2+}$ ($3d^5$) has 5 unpaired electrons. $Fe^{2+}$ ($3d^6$) has 4; $Cr^{2+}$ ($3d^4$) has 4; $Co^{2+}$ ($3d^7$) has 3; $Ni^{2+}$ ($3d^8$) has 2.

Step 4: Conclusion
$Mn^{2+}$ has the maximum number of unpaired electrons, hence the highest magnetic moment. Final Answer: (B)