Q.

Match List-I with List-II                                                                                         [2024]

  List-I (Complex ion):   List-II (Spin only magnetic moment in B.M.)
(A) [Cr(NH3)6]3+ (I) 4.90
(B) [NiCl4]2- (II) 3.87
(C) [CoF6]3- (III) 0.0
(D) [Ni(CN)4]2- (IV) 2.83

 

Choose the correct answer from the options given below:

1 (A)-(I), (B)-(IV), (C)-(II), (D)-(III)  
2 (A)-(II), (B)-(III), (C)-(I), (D)-(IV)  
3 (A)-(II), (B)-(IV), (C)-(I), (D)-(III)  
4 (A)-(IV), (B)-(III), (C)-(II), (D)-(I)  

Ans.

(3)

(A)   [Cr(NH3)6]3+

Oxidation number of Cr = +3

Cr3+=[Ar]3d318

As inner d orbitals are available, it undergoes d2sp3 hybridization.

Orbital diagram of Cr3+ in presence of NH3

It has 3 unpaired electrons. Spin only magnetic moment (μ)=n(n+2)BM=3(3+2)BM=3.87BM

(B)   [NiCl4]2-

Oxidation number of Ni = +2

Ni2+=[Ar]3d818

Cl- is weak field ligand hence does not cause pairing of 3d8 electrons, Ni2+ undergoes sp3 hybridization and lone pairs from Cl- are accommodated in sp3 orbitals.

Orbital diagram of Ni2+ in presence of Cl-

As it contains 2 unpaired electrons. Spin only magnetic moment (μ)=n(n+2)BM=2(2+2)BM=2.82BM

(C)   [CoF6]3-

Oxidation number of Co = +3

Co3+=[Ar]3d618

F-is a weak field ligand. It cannot pair up d electrons. Thus, 4d orbitals are used for sp3d2 hybridization. Six e- pairs from six F- are accommodated in these six sp3d2 orbitals.

Orbital diagram of Co3+ in presence of F-

It has 4 unpaired electrons. Spin only magnetic moment (μ)=n(n+2)BM=4(4+2)BM=4.9BM

(D)    [Ni(CN)4]2-

Oxidation number of Ni = +2

Ni2+=[Ar]3d818

CN- is strong field ligand hence causes pairing of 3d8 electrons, then causes dsp2 hybridization using 3d, 4s, and 4p orbitals.

Orbital diagram of Ni2+ in presence of CN-

It has no unpaired electron. Spin only magnetic moment (μ)=n(n+2)BM=0(0+2)BM=0BM