The metal complex that is diamagnetic is (Atomic number: $\mathrm{Fe}, 26 ; \mathrm{Cu}, 29)$
Solution
$\Rightarrow \mathrm{K}_{3}\left[\mathrm{Cu}(\mathrm{CN})_{4}\right]$ is diamagnetic
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$\mathrm{Cu}(\mathrm{I}) \Rightarrow \mathrm{d}^{10}$ configuration $\Rightarrow$ No unpaired electrons.
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$$\Rightarrow \mathrm{K}_{2}\left[\mathrm{Cu}(\mathrm{CN})_{4}\right], \mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{4}\right]$$ and $\mathrm{K}_{4}\left[\mathrm{FeCl}_{6}\right]$ are paramagnetic in nature
About this question
Subject: Chemistry · Chapter: Coordination Compounds · Topic: Ligands and Coordination Number
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