Match Coordination Complex Shapes and Magnetic Moments

❓ Question

Match the LIST-I with LIST-II

LIST-I (Complex Species)	LIST-II (Shape & Magnetic Moment)
A. $[Ni(CO)_4]$	I. Tetrahedral, $2.8\ BM$
B. $[Ni(CN)_4]^{2-}$	II. Square planar, $0\ BM$
C. $[NiCl_4]^{2-}$	III. Tetrahedral, $5.9\ BM$
D. $[MnBr_4]^{2-}$	IV. Tetrahedral, $0\ BM$

Choose correct match.

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🖼 Question Image

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✍️ Short Explanation

This problem is based on:

👉 Coordination compounds
👉 Hybridization and geometry
👉 Magnetic moment and unpaired electrons.

Main idea:

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

Where:

• $n$ = number of unpaired electrons

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🔷 Step 1 — Analyse $[Ni(CO)_4]$ 💯

Oxidation state of Ni:

$$0$$

Electronic configuration:

$$Ni:3d^84s^2$$

With CO ligand:

$$Ni^0\rightarrow3d^{10}$$

All electrons paired.

Geometry:

$$\boxed{\text{Tetrahedral}}$$

Magnetic moment:

$$\boxed{0\ BM}$$

Thus:

$$A\rightarrow IV$$

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🔷 Step 2 — Analyse $[Ni(CN)_4]^{2-}$

Oxidation state:

$$Ni^{2+}$$

Configuration:

$$3d^8$$

CN$^{-}$ is strong field ligand.

Hence pairing occurs.

Hybridization:

$$dsp^2$$

Geometry:

$$\boxed{\text{Square planar}}$$

All electrons paired.

$$\mu=0\ BM$$

Thus:

$$B\rightarrow II$$

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🔷 Step 3 — Analyse $[NiCl_4]^{2-}$

Oxidation state:

$$Ni^{2+}$$

Configuration:

$$3d^8$$

Cl$^{-}$ is weak field ligand.

No pairing occurs.

Hybridization:

$$sp^3$$

Geometry:

$$\boxed{\text{Tetrahedral}}$$

Number of unpaired electrons:

$$n=2$$

Magnetic moment:

$$\mu=\sqrt{2(2+2)}$$
$$=\sqrt8 \approx2.8\ BM$$

Thus:

$$C\rightarrow I$$

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🔷 Step 4 — Analyse $[MnBr_4]^{2-}$

Oxidation state:

$$Mn^{2+}$$

Configuration:

$$3d^5$$

Br$^{-}$ is weak field ligand.

No pairing.

Geometry:

$$\boxed{\text{Tetrahedral}}$$

Unpaired electrons:

$$n=5$$

Magnetic moment:

$$\mu=\sqrt{5(5+2)}$$
$$=\sqrt{35} \approx5.9\ BM$$

Thus:

$$D\rightarrow III$$

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🔷 Step 5 — Final Matching

$$\boxed{ A-IV,\ B-II,\ C-I,\ D-III }$$

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🔷 Step 6 — JEE Trap Alert 🚨

❌ Strong field aur weak field ligand confuse kar dena

❌ Square planar vs tetrahedral mix kar dena

❌ Magnetic moment formula bhool jaana

Remember:

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

and:

✔ Strong field → pairing

✔ Weak field → no pairing

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✅ Final Answer

$$\boxed{ A-IV,\ B-II,\ C-I,\ D-III }$$

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