MCQ
Consider that a $d ^{6}$ metal ion $\left( M ^{2+}\right)$ forms a complex with aqua ligands, and the spin only magnetic moment of the complex is $4.90$ $BM.$ The geometry and the crystal field stabilization energy of the complex is:
  • A
    tetrahedral and $-1.6 \Delta_{ t }+1 P$
  • tetrahedral and $-0.6 \Delta_{ t }$
  • C
    octahedral and $-1.6 \Delta_{0}$
  • D
    octahedral and $-2.4 \Delta_{0}+2 P$

Answer

Correct option: B.
tetrahedral and $-0.6 \Delta_{ t }$
b
If spin only magnetic moment of the complex is $4.90 BM ,$ it means number of unpaired electrons should be $4.$

$(A)$ In octahedral complex: $\left[ M \left( H _{2} O \right)_{6}\right]^{2+}$

$C.F.S.E.$ $=\left(-0.4 \Delta_{0}\right) \times 4+\left(+0.6 \Delta_{0}\right) \times 2+0 \times P$

$(B)$ In tetrahedral complex: $\left[ M \left( H _{2} O \right)_{4}\right]^{2+}$

$C.F.S.E.$ $=\left(-0.6 \Delta_{t}\right) \times 3+\left(+0.4 \Delta_{t}\right) \times 3+0 \times P$

$=-0.6 \Delta_{ t }$

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