Question

Select the correct order of paramagnetic character among following elements
A. $\text{Mn > Fe > Cr}$
B. $\text{Fe > Zn > Cr}$
C. $\text{Cr > Fe > Zn}$
D. $\text{Cr > Mn > Fe}$

Answer 1

Hint:Magnetic properties develop from the spin as well as the orbital angular momentum of electrons that are present in a compound. Molecular compounds which consist of one or more unpaired electrons are considered to be paramagnetic. The magnitude of para-magnetism is generally expressed as an effective magnetic moment.

Complete answer:
As we know, magnetic properties of any substance can be determined through its electron configuration. If the substance has unpaired electrons, then it is paramagnetic whereas if it comprises all paired electrons, then it is considered to be diamagnetic. So to identify the paramagnetic behaviour of the given elements, let us write their electronic configuration as mentioned below:
\[
  {Cr{\text{ }}\left( {Atomic{\text{ }}No.{\text{ }}24} \right) - \;4{s^1}\;3{d^5}} \\
  {Fe{\text{ }}\left( {Atomic{\text{ }}No.{\text{ }}26} \right) - {\text{ }}4{s^2}\;3{d^6}} \\
  {Zn{\text{ }}\left( {Atomic{\text{ }}No.{\text{ }}30} \right) - \;4{s^2}\;3{d^{10}}} \\
  {Mn{\text{ }}\left( {Atomic{\text{ }}No.{\text{ }}25} \right) - \;4{s^2}\;3{d^5}}
\]
As visible from the electronic configuration, the number of unpaired electrons that are present in \[Cr,{\text{ }}Fe,{\text{ }}Zn{\text{ }}and{\text{ }}Mn\] are 6, 4, 0 and 5 respectively.
We know that greater is the number of the unpaired electrons in an element, greater will be the paramagnetic character of that element.
So, the order of the paramagnetic character among the given elements will be: \[Cr > Fe > Zn\;\] and \[Cr > Mn > Fe\].

Hence, the correct answer is Option C and Option D.

Note:
Magnetic moments can also be calculated by obtaining the information of the number of unpaired electrons. The magnetic moment can be calculated with the following formula:
$\mu = \sqrt {n(n + 2)} $
Here, n = number of unpaired electrons
Paramagnetic materials tend to possess a permanent magnetic moment or permanent dipole moment. Though, if we remove the applied magnetic field, the materials have the ability to lose their magnetism.