Question

Which of the following is more paramagnetic?

• A. ${\mathrm{Fe}}^{2+}$
• B. ${\mathrm{Fe}}^{3+}$
• C. ${\mathrm{Cr}}^{3+}$
• D. ${\mathrm{Mn}}^{3+}$

Answer 1

The correct option is B

${\mathrm{Fe}}^{3+}$

The explanation for correct option:

(b) ${\mathrm{Fe}}^{3+}$

1. When placed in a magnetic field, paramagnetic materials tend to become weakly magnetised in the direction of the magnetizing field.
2. Most atoms with incompletely filled atomic orbitals are paramagnetic due to the presence of unpaired electrons in the substance.
3. Unpaired electrons have a magnetic dipole moment and act like small magnets because of their spin.
4. Electronic Configuration of ${\mathrm{Fe}}^{3+}$: $\left[\mathrm{Ar}\right]3d^5$
5. It has five unpaired electrons in its d orbital.
6. So, it will show maximum paramagnetism.

The explanation for incorrect option:

(a) ${\mathrm{Fe}}^{2+}$

1. Electronic configuration of ${\mathrm{Fe}}^{2+}$: $\left[\mathrm{Ar}\right]3d^6$
2. It has four unpaired electrons.
3. So, it will be less paramagnetic than ${\mathrm{Fe}}^{3+}$

(c) ${\mathrm{Cr}}^{3+}$

1. Electronic configuration of ${\mathrm{Cr}}^{3+}$: $\left[\mathrm{Ar}\right]3d^3$
2. It has 3 unpaired electrons.
3. So, it will be less paramagnetic than both ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$

(d) ${\mathrm{Mn}}^{3+}$

1. Electronic configuration of ${\mathrm{Mn}}^{3+}$ : $\left[\mathrm{Ar}\right]3d^4$
2. It has four unpaired electrons.
3. So, it will be less paramagnetic than ${\mathrm{Fe}}^{3+}$

Therefore, Option (b) is correct, ${\mathrm{Fe}}^{3+}$is most paramagnetic.