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Question: Answered & Verified by Expert
Which one of the following transition metal ions is diamagnetic?
ChemistryCoordination CompoundsJIPMERJIPMER 2012
Options:
  • A $\mathrm{Co}^{2+}$
  • B $\mathrm{Ni}^{2+}$
  • C $\mathrm{Cu}^{2+}$
  • D $\mathrm{Zn}^{2+}$
Solution:
1011 Upvotes Verified Answer
The correct answer is: $\mathrm{Zn}^{2+}$
Transition metal ion having absence of unpaired electron is diamagnetic.
(1) $\mathrm{Co}^{2+}=[\mathrm{Ar}] 3 d^7$ (three unpaired electrons)
(2) $\mathrm{Ni}^{2+}=[\mathrm{Ar}] 3 d^8$ (two unpaired electrons)
(3) $\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 d^9$ (one unpaired electron)
(4) $\mathrm{Zn}^{2+}=[\mathrm{Ar}] 3 d^{10}$ (no unpaired electron)
Thus, $\mathrm{Zn}^{2+}$ is diamagnetic.

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