JEE Main · 2022 · Shift-IIeasyDNF-014

The metal ion (in gaseous state) with lowest spin-only magnetic moment value is:

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

Options

a
$\text{V}^{2+}$
b
$\text{Ni}^{2+}$
✓
c
$\text{Cr}^{2+}$
d
$\text{Fe}^{2+}$

Correct Answerb

$\text{Ni}^{2+}$

Detailed Solution

$\mu = \sqrt{n(n+2)}$ BM

| Ion | M²⁺ Config | Unpaired e⁻ | $\mu$ (BM) | |-----|------------|-------------|------------| | V²⁺ | $3d^3$ | 3 | 3.87 | | Ni²⁺ | $3d^8$ | 2 | 2.83 | | Cr²⁺ | $3d^4$ | 4 | 4.90 | | Fe²⁺ | $3d^6$ | 4 | 4.90 |

$\text{Ni}^{2+}$ ( $3d^8$ ) has only 2 unpaired electrons → lowest $\mu = \sqrt{8} = 2.83$ BM.

Answer: Option (2) — $\text{Ni}^{2+}$

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