The calculated spin-only magnetic moment values in BM for [FeCl4]- and [Fe(CN)6]3- are
- 5.9 BM,1.732 BM
- 4.89 BM,1.732 BM
- 3.87 BM,1.732 BM
- 1.732 BM,2.82 BM
The Correct Option is A
Solution and Explanation
Let’s correctly determine the spin-only magnetic moment for the given complexes:
- [FeCl4]−:
• Oxidation state of Fe: +3 (Fe → +3 because Cl− × 4 = −4 and overall charge = −1 → Fe = +3)
• Fe3+ → 3d5 configuration
• Cl− is a weak field ligand ⇒ high spin ⇒ 5 unpaired electrons
• Spin-only magnetic moment:
\(\mu = \sqrt{5(5+2)} = \sqrt{35} \approx 5.92\ \mu_B\) - [Fe(CN)6]3−:
• Oxidation state of Fe: +3 (same logic)
• Fe3+ → 3d5 configuration
• CN− is a strong field ligand ⇒ low spin ⇒ 1 unpaired electron
• Spin-only magnetic moment:
\(\mu = \sqrt{1(1+2)} = \sqrt{3} \approx 1.732\ \mu_B\)
Correct answer: Option (A): 5.9 BM, 1.732 BM
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Concepts Used:
D and F Block Elements
The d-block elements are placed in groups 3-12 and F-block elements with 4f and 5f orbital filled progressively. The general electronic configuration of d block elements and f- block elements are (n-1) d 1-10 ns 1-2 and (n-2) f 1-14 (n-1) d1 ns2 respectively. They are commonly known as transition elements because they exhibit multiple oxidation states because of the d-d transition which is possible by the availability of vacant d orbitals in these elements.
They have variable Oxidation States as well as are good catalysts because they provide a large surface area for the absorption of reaction. They show variable oxidation states to form intermediate with reactants easily. They are mostly lanthanoids and show lanthanoid contraction. Since differentiating electrons enter in an anti-penultimate f subshell. Therefore, these elements are also called inner transition elements.
Read More: The d and f block elements