Chemistry · Coordination Compounds

JEE Main 2024 — 5 April, Shift 1 — Question 67

Which one of the following complexes will exhibit the least paramagnetic behaviour?

[Atomic number, $\mathrm{Cr}=24, \mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27$ ]

Option A:
$\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$
Correct
Option B:
$\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$
Option C:
$\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$
Option D:
$\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$

Answer: A

	Number of unpaired e	$\mu =\sqrt{\text{n}\left( \text{n}+2 \right)}$ B.M.
${{\left[ \text{Co}{{\left( {{\text{H}}_{2}}\text{O} \right)}_{6}} \right]}^{2+}}$	3	3.87
${{\left[ \text{Fe}{{\left( {{\text{H}}_{2}}\text{O} \right)}_{6}} \right]}^{2+}}$	4	4.89
${{\left[ \text{Mn}{{\left( {{\text{H}}_{2}}\text{O} \right)}_{6}} \right]}^{2+}}$	5	5.92
${{\left[ \text{Cr}{{\left( {{\text{H}}_{2}}\text{O} \right)}_{6}} \right]}^{2+}}$	4	4.89

Answer key and solution verified before publishing.

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