Question:medium

The spin only magnetic moment of\(\left[ Mn \left( H _2 O \right)_6\right]^{2+}\) complexes is ____ BM (Nearest integer) (Given: Atomic no of $Mn$ is 25 )

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Remember the formula for spin-only magnetic moment: \(μ_{spin} =\sqrt{n(n + 2)}\) B.M., where n is the number of unpaired electrons. The strength of the ligand determines the pairing of d-electrons.

Updated On: Mar 31, 2026
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Correct Answer: 6

Solution and Explanation

The spin-only magnetic moment of a complex is calculated using the formula:
\(\mu = \sqrt{n(n+2)}\) Bohr Magneton (BM), where n is the number of unpaired electrons.

Step 1: Determine the electron configuration of Mn.
Manganese (Mn) has the atomic number 25, so its electron configuration is [Ar] 3d^5 4s^2.

Step 2: Analyze the complex \([Mn(H_2O)_6]^{2+}\).
In this complex, Mn is in the +2 oxidation state. This means it loses two electrons, typically from the 4s sublevel, resulting in the configuration:
[Ar] 3d^5.

Step 3: Calculate the number of unpaired electrons.
The 3d^5 configuration implies five unpaired electrons because each 3d orbital contains one electron.
Thus, n = 5.

Step 4: Calculate the magnetic moment.
Using the formula:
\(\mu = \sqrt{5(5+2)} = \sqrt{35} \approx 5.92\) BM.
The nearest integer is 6 BM.

Verification: Check if this value fits the given range (6,6). It does, confirming our solution.

The spin-only magnetic moment of \([Mn(H_2O)_6]^{2+}\) is 6 BM.

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