Question

Which one of the following transition metal ion is diamagentic?

• A. ${\mathrm{Zn}}^{2+}$
• B. ${\mathrm{Ni}}^{2+}$
• C. ${\mathrm{Cu}}^{2+}$
• D. ${\mathrm{Co}}^{2+}$

Answer 1

The correct option is A

${\mathrm{Zn}}^{2+}$

The explanation for the correct option:

(A) ${\mathbf{Zn}}^{\mathbf{2}\mathbf{+}}$

• Diamagnetic materials have no unpaired electrons in their outermost orbital and are repelled by a magnetic field.
• Paramagnetic materials have at least one or more unpaired electrons in their outermost shell and it is attracted to magnetism.
• The atomic number of zinc is $30$ and its electronic configuration is : $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{2}3{\mathrm{d}}^{10}$
• Electronic configuration of ${\mathrm{Zn}}^{2+}$ is : $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{0}3{\mathrm{d}}^{10}$
• ${\mathrm{Zn}}^{2+}$ has fully filled orbital in$3\mathrm{d}$ orbital and $4\mathrm{s}$is completely empty.

• Since it has no unpaired electrons, it is a diamagnetic ion.

The explanation for incorrect options:

B) ${\mathbf{Ni}}^{\mathbf{2}\mathbf{+}}$

• The atomic number of nickel is $28$
• The electronic configuration of nickel is: $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{2}3{\mathrm{d}}^8$
• Electronic configuration of ${\mathrm{Ni}}^{2+}$is: $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{0}3{\mathrm{d}}^8$
• It has two unpaired electrons in it. Therefore, it is paramagnetic.

C) ${\mathbf{Cu}}^{\mathbf{2}\mathbf{+}}$

• The atomic number of copper is $29$
• The electronic configuration of copper is: $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{1}3{\mathrm{d}}^{10}$
• Electronic configuration of ${\mathrm{Cu}}^{2+}$is:$\left[\mathrm{Ar}\right]4{\mathrm{s}}^{0}3{\mathrm{d}}^9$
• It has one unpaired electron and hence is paramagnetic in nature.

D) ${\mathbf{Co}}^{\mathbf{2}\mathbf{+}}$

• The atomic number of Cobalt is $27$
• The electronic configuration of cobalt is: $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{2}3{\mathrm{d}}^7$
• Electronic configuration of ${\mathrm{Co}}^{2+}$ is: $\left[\mathrm{Ar}\right]4{\mathrm{s}}^{0}3{\mathrm{d}}^7$
• It has three unpaired electrons and hence is paramagnetic in nature.

Hence, the correct option is A) ${\mathbf{Zn}}^{\mathbf{2}\mathbf{+}}$