NCERT Class XII Chemistry
Chapter - The d- and f-Block Elements
Questions with Solutions

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Question : 38
Total: 49
What can be inferred from the magnetic moment values of the following complex species?
 Example  Magnetic Moment (BM)  
  K4[ Mn(CN)6 ]  2.2  
 [Fe(H2O)6]2+  5.3  
 K2[MnCl4]  5.9  
Solution:  
Magnetic Moment (µ)=n(n+2)BM
When n=1,
µ=1(1+2)=3=1.73 BM2
When n=2,
µ=2(2+2)=8=2.83 BM3
When n=3,
µ=3(3+2)=15=3.87BM4
When n4,
µ=4(4+2)=24=4.90BM=5
When n=5,
µ=5(5+2)=35=5.92BM6
K4[Mn(CN)6]: Oxidation state of Mn is +2, Mn2+ has an electronicconfiguration of [Ar]3d5.
As µ = 2.2 BM which corresponds to one unpaired electron. The orbitaldiagramfor Mn2+ is
[Fe(H2O)6]2+:µ = 5.3 BM corresponds to 4 unpaired electrons. Theconfiguration of Fe2+ ions is [Ar]3d6and orbital diagram is
K2[MnCl4],: µ = 5.9 BM, Mn2+ ion has 5 unpaired electrons. Its orbitaldiagram is
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