Paramagnetism and Diamagnetism: Videos & Practice Problems

In chemistry, the behavior of electrons within orbitals is governed by the Pauli exclusion principle, which states that an orbital can hold a maximum of two electrons with opposite spins. Substances can be classified as either paramagnetic or diamagnetic based on their electron configurations. Paramagnetic substances have at least one unpaired electron in an orbital, making them responsive to magnetic fields. Conversely, diamagnetic substances have all electrons paired within their orbitals, rendering them unaffected by magnetic fields. Understanding whether elements or ions are paramagnetic or diamagnetic is crucial when determining their electron configurations, as it reflects the arrangement of electrons and their magnetic properties.

Paramagnetism vs Diamagnetism

In atomic theory, understanding the behavior of electrons in orbitals is crucial, particularly when discussing the concepts of paramagnetism and diamagnetism. An orbital can accommodate a maximum of two electrons, which must have opposite spins, as dictated by the Pauli exclusion principle. This principle is fundamental in determining the magnetic properties of substances.

Paramagnetic materials contain at least one unpaired electron in their orbitals, making them responsive to external magnetic fields. For instance, in an s orbital where all electrons are paired, the substance would not exhibit paramagnetism. However, if we examine p orbitals and find an unpaired electron, the substance becomes paramagnetic. The presence of even a single unpaired electron is sufficient for a material to be classified as paramagnetic.

In contrast, diamagnetic substances have all their electrons paired within their orbitals. This means that every orbital, whether s or p, contains two electrons with opposite spins, resulting in no unpaired electrons. Consequently, diamagnetic materials are not influenced by magnetic fields.

When determining the electron configurations of elements or ions, it is essential to identify whether they are paramagnetic or diamagnetic. A paramagnetic element or ion will have at least one unpaired electron, while a diamagnetic one will have all electrons paired. This distinction is vital for predicting the magnetic behavior of various substances.

Which of the following atoms has the most unpaired electrons? 

• A. Co
• B. Mn
• C. Ti
• D. Zn
• E. Fe

Answer: (B)

Write the condensed electron configuration for the nickel (III) ion and state if it is paramagnetic or diamagnetic.

• A. $\left\lbrack Ar\right\rbrack3d^7$; Diamagnetic
• B. $\left\lbrack Ar\right\rbrack3d^7$; Paramagnetic
• C. $\left\lbrack Ar\right\rbrack3d^8$; Paramagnetic
• D. $\left\lbrack Ar\right\rbrack3d^74s^1$; Paramagnetic

Answer: (B)

Write the condensed electron configuration for the copper (I) ion and is it magnetic?

• A. $\left[ Ar\right]4s^23d^9$ ; Diamagnetic
• B. $\left[Ar\right]3d^{10}$ ; Diamagnetic
• C. $\left[ Ar\right]4s^23d^9$ ; Paramagnetic
• D. $\left[ Ar\right]3d^{10}$ ; Paramagnetic

Answer: (B)

Here’s what students ask on this topic:

What is paramagnetic?

Paramagnetic materials are those that are attracted by an external magnetic field and form internal, induced magnetic fields in the direction of the applied magnetic field. This attraction is due to the presence of unpaired electrons in the material. Each unpaired electron has a magnetic moment, which is a magnetic field that they generate. When an external magnetic field is applied, these magnetic moments tend to align themselves in the direction of the field, causing the material to be drawn towards it.

However, once the external magnetic field is removed, paramagnetic materials lose their magnetization since the thermal motion at room temperature quickly randomizes the electron spin orientations. This is in contrast to ferromagnetic materials, which can retain their magnetization. Paramagnetic properties are temperature-dependent, and the susceptibility of paramagnetic materials to magnetic fields decreases with increasing temperature. Examples of paramagnetic materials include aluminum, platinum, manganese, and certain compounds like oxygen gas.

What is diamagnetic?

Diamagnetism is a property of all materials and refers to their natural tendency to oppose an external magnetic field. When a diamagnetic material is placed in a magnetic field, it will induce a magnetic moment in the opposite direction, causing a repulsive effect. This occurs because the electrons in the diamagnetic material rearrange their orbits slightly, which generates tiny currents that produce the opposing magnetic field. The effect is generally very weak, and therefore, diamagnetic materials are not attracted to magnets.

One of the most common examples of a diamagnetic material is water. Other examples include copper, gold, and mercury. Diamagnetism is a quantum mechanical effect that persists only as long as an external magnetic field is present. Unlike ferromagnetism, where materials can retain their magnetization, once the external field is removed, diamagnetic materials revert to a non-magnetic state.

How do you determine if a substance is paramagnetic or diamagnetic?

To determine whether a substance is paramagnetic or diamagnetic, you need to look at the electron configuration of its atoms. A substance is paramagnetic if it has at least one unpaired electron in its electron configuration. These unpaired electrons create magnetic moments that can align with an external magnetic field, making the substance attracted to the field.

On the other hand, a substance is diamagnetic if all of its electrons are paired. Paired electrons have opposite spins that cancel out each other's magnetic moment, resulting in no net magnetic moment. Diamagnetic substances are weakly repelled by a magnetic field.

A simple test to determine this property is to place the substance in an inhomogeneous magnetic field. Paramagnetic substances will move towards the stronger part of the field, while diamagnetic substances will be repelled by it. Additionally, you can consult a material's electron configuration or use magnetic susceptibility measurements to confirm its magnetic properties.

How can one tell the difference between paramagnetic and diamagnetic?

To differentiate between paramagnetic and diamagnetic materials, you need to consider their response to magnetic fields due to the alignment of their electron spins. Paramagnetic materials have unpaired electrons in their atomic or molecular structures, which means they have magnetic moments that can align with an external magnetic field. As a result, paramagnetic materials are attracted to magnetic fields, although the attraction is relatively weak.

On the other hand, diamagnetic materials have only paired electrons, which means they do not have a net magnetic moment. When exposed to a magnetic field, diamagnetic materials create an induced magnetic field in a direction opposite to that of the applied magnetic field. This causes a repulsive effect, but it's very subtle. In essence, diamagnetic materials are repelled by magnetic fields, but the effect is so weak that it's often only detectable with sensitive instruments.

A simple test to distinguish between the two is to place the material in a non-uniform magnetic field and observe its behavior: paramagnetic materials will move towards the stronger part of the field (attracted), while diamagnetic materials will move towards the weaker part (repelled).