Question

Among Sc, Ti, Mn and Co, calculate the spin-only magnetic moment in the \( +2 \) oxidation state of the metal having the highest heat of atomisation.

• A. 4.9 B.M.
• B. 5.9 B.M.
• C. 2.9 B.M.
• D. 3.9 B.M.

Hint:

The magnetic moment for a transition metal in its oxidation state is determined by the number of unpaired electrons in its d-orbitals.

Answer 1

The Correct Option is A

The magnetic moment is given by: \[ \mu = \sqrt{n(n+2)} \, \text{B.M.} \] Where \( n \) is the number of unpaired electrons. For \( \text{Sc}^{2+} \) (3d\(^1\)), \( \mu = 1 \, \text{B.M.} \). For \( \text{Ti}^{2+} \) (3d\(^2\)), \( \mu = \sqrt{2(2+2)} = \sqrt{8} = 2.83 \, \text{B.M.} \). 

For \( \text{Mn}^{2+} \) (3d\(^5\)), \( \mu = \sqrt{5(5+2)} = \sqrt{35} = 5.92 \, \text{B.M.} \). For \( \text{Co}^{2+} \) (3d\(^7\)), \( \mu = \sqrt{7(7+2)} = \sqrt{63} = 7.94 \, \text{B.M.} \). 

Thus, the highest magnetic moment is for \( \text{Mn}^{2+} \), which has \( 5.9 \, \text{B.M.} \).