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Chemistry · Coordination Compounds

JEE Main 2025 — 7 April, Evening Shift — Question 7

The number of unpaired electrons responsible for the paramagnetic nature of the following complex species are

respectively: [Fe(CN)6]3−,[FeF6]3−,[CoF6]3−,[Mn(CN)6]3−\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-},\left[\mathrm{FeF}_{6}\right]^{3-},\left[\mathrm{CoF}_{6}\right]^{3-},\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-}

  1. Option A:

    1,5,4,21,5,4,2

    Correct
  2. Option B:

    1,4,4,21,4,4,2

  3. Option C:

    1,1,4,21,1,4,2

  4. Option D:

    1,5,5,21,5,5,2

Answer: A

Step-by-step solution

[Fe(CN)6]3−⇒Fe3+,d5,t2 g5eg0\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-} \Rightarrow \mathrm{Fe}^{3+}, \mathrm{d}^{5}, \mathrm{t}_{2 \mathrm{~g}}^{5} \mathrm{e}_{\mathrm{g}}^{0}

⇒1 unpaired electron \Rightarrow 1 \text { unpaired electron }

[FeF6]3−⇒Fe3+,d5,t2 g3eg2⇒5\left[\mathrm{FeF}_{6}\right]^{3-} \Rightarrow \mathrm{Fe}^{3+}, \mathrm{d}^{5}, \mathrm{t}_{2 \mathrm{~g}}^{3} \mathrm{e}_{\mathrm{g}}^{2} \Rightarrow 5 unpaired electrons

[CoF6]3−⇒Co3+,d6,t2 g4eg2⇒4\left[\mathrm{CoF}_{6}\right]^{3-} \Rightarrow \mathrm{Co}^{3+}, \mathrm{d}^{6}, \mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{2} \Rightarrow 4 unpaired electrons

[Mn(CN)6]3−⇒Mn3+,d4,t2 g4eg0\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-} \Rightarrow \mathrm{Mn}^{3+}, \mathrm{d}^{4}, \mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{0} ⇒2\Rightarrow 2 unpaired electrons

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
7 April, Evening Shift
Subject
Chemistry
Chapter
Coordination Compounds
Topic
Properties and importance of Coordination Complexes

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