Question

Which one of the following transition metal ions is diamagnetic?

• A. $C{o}^{2+}$
• B. $N{i}^{2+}$
• C. $C{u}^{2+}$
• D. $Z{n}^{2+}$

Answer 1

Answer: (D)

Transition metal ion having absence of unpaired electron is diamagnetic.
[a] $C{o}^{2+}=[Ar]3d^7$ (three unpaired electrons)
[b] $N{i}^{2+}=[Ar]3d^8$ (two unpaired electrons)
[c] $C{u}^{2+}=[Ar]3d^9$ (one unpaired electron)
[d] $Z{n}^{2+}=[Ar]3d^{10}$ (no unpaired electron)
Thus, $Z{n}^{2+}$ is diamagnetic.