The number of paramagnetic species from the following is ___________. [Ni(CN)_4]^2-, [Ni(CO)_4], [NiCl_4]^2-, [Fe(CN)_6]^4-, [Cu(NH_3)_4]^2+ [Fe(CN)_6]^3- and [Fe(H_2O)_6]^2+

The number of paramagnetic species from the following is… — JEE Main 2023 Chemistry PYQ

The number of paramagnetic species from the following is ___________.

[\text{Ni}(\text{CN})_4]^{2-}

[\text{Ni}(\text{CO})_4]

[\text{NiCl}_4]^{2-}

[\text{Fe}(\text{CN})_6]^{4-}

[\text{Cu}(\text{NH}_3)_4]^{2+}

[\text{Fe}(\text{CN})_6]^{3-}

and

[\text{Fe}(\text{H}_2\text{O})_6]^{2+}

Show answer and solution

Answer: 4

Solution

Analyze each complex for unpaired electrons:

1. [Ni(CN)₄]²⁻: Ni²⁺ (d⁸), CN⁻ is strong field → square planar, all 8 d-electrons paired → diamagnetic

2. [Ni(CO)₄]: Ni⁰ (d¹⁰), all electrons paired → diamagnetic

3. [NiCl₄]²⁻: Ni²⁺ (d⁸), Cl⁻ is weak field → tetrahedral, 2 unpaired electrons → paramagnetic

4. [Fe(CN)₆]⁴⁻: Fe²⁺ (d⁶), CN⁻ strong field → low spin, all 6 d-electrons paired → diamagnetic

5. [Cu(NH₃)₄]²⁺: Cu²⁺ (d⁹), 1 unpaired electron → paramagnetic

6. [Fe(CN)₆]³⁻: Fe³⁺ (d⁵), CN⁻ strong field → low spin, 1 unpaired electron → paramagnetic

7. [Fe(H₂O)₆]²⁺: Fe²⁺ (d⁶), H₂O weak field → high spin, 4 unpaired electrons → paramagnetic

Paramagnetic species: [NiCl₄]²⁻, [Cu(NH₃)₄]²⁺, [Fe(CN)₆]

[JEE Main 2023 · 25 Jan · Shift 1]

JEE Main 2023 Chemistry question on Coordination Compounds