Question

Identify the lanthanoid that exhibits zero effective magnetic moment in +3 state.

• A. Ho
• B. Lu
• C. Pr
• D. Er

Hint:

$La^{3+}$ ($4f^0$) and $Lu^{3+}$ ($4f^{14}$) are the only lanthanoid ions with zero magnetic moment.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
A zero effective magnetic moment (\( \mu_{eff} = 0 \)) occurs when an ion has no unpaired electrons (all electrons are paired).
Step 2: Detailed Explanation:
The electronic configuration of lanthanoids in the +3 oxidation state involves losing 2 electrons from the \( 6s \) orbital and 1 from the \( 5d \) or \( 4f \) orbital.
- \( Ho^{3+} \): Has unpaired electrons in \( 4f \) subshell.
- \( Lu^{3+} \): Lutetium (\( Z = 71 \)) has ground state config \( [Xe] 4f^{14} 5d^{1} 6s^{2} \). In \( Lu^{3+} \), it loses \( 5d^1 \) and \( 6s^2 \), leaving \( [Xe] 4f^{14} \). The \( 4f \) subshell is completely filled, meaning \( n = 0 \).
- \( Pr^{3+} \): Has unpaired electrons.
- \( Er^{3+} \): Has unpaired electrons.
Since \( Lu^{3+} \) has zero unpaired electrons, its magnetic moment is zero.
Step 3: Final Answer:
Lutetium (Lu) exhibits zero effective magnetic moment in the +3 state.