Question

Which cation from following exhibits no magnetic moment?

• A. $\text{Cr}^{3+}$
• B. $\text{Sc}^{3+}$
• C. $\text{Cu}^{2+}$
• D. $\text{V}^{3+}$

Hint:

The magnetic moment formula is $\mu = \sqrt{n(n+2)}$ Bohr Magnetons (BM), where $n$ is the number of unpaired electrons. If $n=0$, then $\mu=0$! Ions with $d^0$ or $d^{10}$ configurations always have zero magnetic moment.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Magnetic moment arises from the presence of unpaired electrons. If an ion has a completely empty or completely filled d-subshell, it will have zero unpaired electrons ($n=0$) and thus no magnetic moment.

Step 2: Formula Application:
Electronic configuration of Scandium ($Z=21$): $[Ar] 3d^1 4s^2$.

Step 3: Explanation:
When Scandium forms the $Sc^{3+}$ ion, it loses all three valence electrons. $Sc^{3+}$ configuration: $[Ar] 3d^0 4s^0$. Since there are no electrons in the d-orbitals, $n = 0$. Magnetic moment $\mu = \sqrt{0(0+2)} = 0$ BM.

Step 4: Final Answer:
The cation $Sc^{3+}$ exhibits no magnetic moment.