Question

Which of the following species would you expect tobe diamagnetic and which paramagnetic? (a) \(\mathrm{K}^{+}=\) (b) \(\mathrm{Cr}^{3+} ;\) (c) \(\mathrm{Zn}^{2+} ;\) (d) \(\mathrm{Cd} ;\) (e) \(\mathrm{Co}^{3+} ;\) (f) \(\mathrm{Sn}^{2+} ;\) (g) Br.

Short answer

\(K^+\), \(Zn^{2+}\), \(Cd\), and \(Br\) are diamagnetic, while \(Cr^{3+}\), \(Co^{3+}\), and \(Sn^{2+}\) are paramagnetic.

Step-by-step solution

Determine the Electronic Configuration

Write down the electronic configuration for each species. \n- The electronic configuration of \(K\) is \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^1\).\nSo, \(K^+\) has lost one electron and will have the configuration: \(1s^2 2s^2 2p^6 3s^2 3p^6\).\n- \(Cr^{3+}\) is formed by losing three electrons from \(Cr\), whose configuration is: \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1\).\n- \(Zn^{2+}\) and \(Cd\) have the same configuration as \(Cd\), which is: \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^2\).\n- The electronic configuration of \(Co\) is \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^7 4s^2\), so \(Co^{3+}\) is formed by losing three electrons.\n- The electronic configuration for \(Sn^{2+}\) is gotten by first writing that of \(Sn\) and removing two electrons.\n- \(Br\)'s electronic configuration is: \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^5\).

Determine Whether Each Species is Diamagnetic or Paramagnetic

Check each species' electron configuration to see if there are unpaired electrons.\n- \(K^+\), \(Zn^{2+}\), \(Cd\), and \(Br\) all have paired electrons, so they're diamagnetic.\n- \(Cr^{3+}\), \(Co^{3+}\), and \(Sn^{2+}\) have unpaired electrons, so they're paramagnetic.

Key concepts

Diamagnetism

Diamagnetism is a property of materials where they are repelled by a magnetic field. This happens when all the electrons in an atom are paired. In a paired electron arrangement, their magnetic fields cancel each other out. This lack of net magnetic moment means that the material does not retain any magnetization on its own.
Some key points about diamagnetism include:

• It is a weak form of magnetism.
• All substances exhibit some form of diamagnetism, but it is often overpowered by other forms of magnetism like paramagnetism or ferromagnetism.
• Diamagnetic materials create an induced magnetic field in a direction opposite to an externally applied magnetic field.

In the context of electron configurations, species such as - \(K^+\), which has an electron configuration of \(1s^2 2s^2 2p^6 3s^2 3p^6\), - \(Zn^{2+}\), and - \(Cd\) are all considered diamagnetic.
This is because they only have paired electrons in their outer shells, leading to no net magnetic moment.

Paramagnetism

Paramagnetism refers to the tendency of some materials to be attracted to a magnetic field due to the presence of unpaired electrons. These unpaired electrons have a net magnetic moment because their spins are not canceled out. As a result, paramagnetic materials are weakly attracted to magnetic fields.
Essential features of paramagnetism are:

• It is stronger than diamagnetism but weaker than ferromagnetism.
• The materials become magnetized in the presence of an external magnetic field and revert to their non-magnetized state once the external field is removed.

For example, species like
- \(Cr^{3+}\), which has an electron configuration where unpaired electrons are present, - \(Co^{3+}\), and - \(Sn^{2+}\)
will exhibit paramagnetic behaviors due to these unpaired electrons. The presence of even a single unpaired electron can give rise to this property, making the material engage with magnetic fields.

Unpaired Electrons

Unpaired electrons are electrons that are alone in an orbital without a matching electron of opposite spin. They significantly influence the magnetic properties of an atom or molecule.
Understanding electron configurations is fundamental in identifying unpaired electrons. Here are a few things to remember:

• Each electron in an atom's orbit can either be paired or unpaired.
• When electrons are unpaired, they contribute to magnetic properties like paramagnetism.

To determine if a species will be paramagnetic or diamagnetic, you need to look at its electron configuration.
For instance, - \(Cr^{3+}\) with the electron configuration having unpaired electrons in the 3d-orbital will be paramagnetic.
Whereas, - \(Cd\) and - \(Zn^{2+}\) show paired electrons in all their orbitals, indicating they are diamagnetic.
The presence or absence of unpaired electrons ultimately decides whether a material will be attracted or repelled by a magnetic field.