Of the following complex ions, which is diamagnetic in nature?

Of the following complex ions, which is diamagnetic in nature?
  1. $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$
  2. $\left[\mathrm{CuCl}_4\right]^{2-}$
  3. $\left[\mathrm{CoF}_6\right]^{3-}$
  4. $\left[\mathrm{NiCl}_4\right]^{2-}$

Solution

Electronic configuration of $\mathrm{Ni}^{2+}$ in $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$ $\mathrm{Ni}^{2+}$ has $d s p^2$ hybridisation, as $\mathrm{CN}^{-}$is a strong field ligand. $\therefore\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$ is diamagnetic (becasue of the absence of unpaired electrons).

Asked in: NEET 2011 (Screening)

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