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Question
Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following:
\[\ce{[FeF6]^{3-}, [Fe(H2O)6]^{2+}, [Fe(CN)6]^{4-}}\]
Solution
(1) \[\ce{FeF^{3-}6}\]:
\[\ce{Fe^{3+} = 3d^5}\]
Number of unpaired electrons = 5
Magnetic moment = `sqrt(5(5 + 2))` = 5.92 BM
(2) \[\ce{[Fe(H2O)6]^{2+}}\]:
\[\ce{Fe^{2+} = 3d^6}\]
Number of unpaired electrons = 4
Magnetic moment = `sqrt(4(4 + 2))` = 4.9 BM
(3) \[\ce{[Fe(CN)6]^{4-}}\]:
\[\ce{Fe^{2+} = 3d^6}\]
Since CN– is a strong field ligand all the electrons get paired.
No unpaired electrons so diamagnetic.
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| Column I (Complex ion) | Column II (Hybridisation, number of unpaired electrons) |
| A. \[\ce{[Cr(H2O)6]^{3+}}\] | 1. dsp2, 1 |
| B. \[\ce{[Co(CN)4]^{2-}}\] | 2. sp3d2, 5 |
| C. \[\ce{[Ni(NH3)6]^{2+}}\] | 3. d2sp3, 3 |
| D. \[\ce{[MnF6]^{4-}}\] | 4. sp3, 4 |
| 5. sp3d2, 2 |
Considering crystal field theory, strong-field ligands such as CN–:
The correct order of increasing crystal field strength in following series:
The magnitude of CFSE depends upon ______
For octahedral Mn(II) and tetrahedral Ni(II) complexes, consider the following statements:
(i) Both the complexes can be high spin.
(ii) Ni(II) complex can very rarely below spin.
(iii) With strong field Ligands, Mn(II) complexes can be low spin.
(iv) Aqueous solution of Mn (II) ions is yellow in colour.
The correct statements are:
