Question

What is the approximate magnetic moment of \(Mn^{2+}\)?

• A. 4.9 BM
• B. 5.9 BM
• C. 6.9 BM
• D. 3.9 BM

Hint:

Magnetic moment increases with the number of unpaired electrons. Transition metal ions with half-filled \(d\)-orbitals often show strong paramagnetism.

Answer 1

The Correct Option is B

Concept: The magnetic moment of transition metal ions arises mainly due to the presence of unpaired electrons. The greater the number of unpaired electrons, the larger the magnetic moment. The magnetic moment is calculated using the spin-only formula: \[ \mu = \sqrt{n(n+2)} \, \text{BM} \] where \(n\) is the number of unpaired electrons.

Step 1: Electronic configuration of Mn. Atomic number of Mn = 25 \[ Mn: [Ar]\,3d^5\,4s^2 \]

Step 2: Electronic configuration of \(Mn^{2+}\). Two electrons are removed from the \(4s\) orbital. \[ Mn^{2+}: [Ar]\,3d^5 \] This configuration contains 5 unpaired electrons.

Step 3: Apply the magnetic moment formula. \[ \mu = \sqrt{5(5+2)} \] \[ \mu = \sqrt{35} \] \[ \mu \approx 5.9 \, BM \] Thus, the approximate magnetic moment of \(Mn^{2+}\) is 5.9 BM.