Paramagnetism

Definition

Paramagnetism is a form of magnetism that occurs in materials with unpaired electrons, leading to a net magnetic moment that is attracted to an external magnetic field. This property arises from the presence of unpaired electrons in the d or f orbitals of transition metals and lanthanides, causing these materials to exhibit a weak magnetic behavior that can be measured. Paramagnetic substances can be distinguished from diamagnetic ones, which have all paired electrons and exhibit no net magnetic moment.

5 Must Know Facts For Your Next Test

1. Paramagnetism increases with temperature because thermal energy can cause more unpaired electrons to align with an external magnetic field.
2. Transition metal complexes often display paramagnetic properties due to their d-orbitals, where unpaired electrons are common.
3. The degree of paramagnetism in a substance can be quantified using Curie's law, which relates magnetic susceptibility to temperature.
4. Unlike ferromagnetic materials, which retain magnetization after the external field is removed, paramagnetic materials only exhibit magnetism while within an external magnetic field.
5. Certain ligands can influence the number of unpaired electrons in coordination compounds, thus affecting their overall paramagnetic behavior.

Review Questions

• How does the presence of unpaired electrons contribute to the paramagnetic properties of a substance?
  • The presence of unpaired electrons in a substance creates a net magnetic moment because these electrons contribute to the material's overall magnetic behavior. When exposed to an external magnetic field, these unpaired electrons tend to align with the field, causing the substance to be attracted to it. This attraction is what characterizes paramagnetism and distinguishes it from other types of magnetism, such as diamagnetism, where all electrons are paired.
• Discuss how crystal field theory explains the differences in magnetic properties among various coordination compounds.
  • Crystal field theory helps explain the differences in magnetic properties by analyzing how the arrangement of ligands around a central metal ion affects electron distribution in its d-orbitals. In octahedral complexes, for example, the splitting of d-orbitals can lead to scenarios where some orbitals contain unpaired electrons while others are filled. Depending on factors like ligand strength and geometry, this can result in either paramagnetic or diamagnetic behavior. Strong field ligands tend to pair up electrons more than weak field ligands, which directly influences the compound's overall magnetism.
• Evaluate how temperature affects paramagnetism in transition metal complexes and the implications for practical applications.
  • Temperature plays a crucial role in paramagnetism as it influences the alignment of unpaired electrons. As temperature increases, thermal energy can disrupt the alignment of these electrons with an external magnetic field, leading to decreased magnetic susceptibility. This relationship has practical applications, particularly in fields like magnetic resonance imaging (MRI) and material science, where understanding how temperature affects the magnetism of coordination compounds is essential for optimizing their use in various technologies.

Related terms

Unpaired Electrons: Electrons that are alone in an orbital, contributing to the magnetic properties of an atom or ion, such as in paramagnetic materials.

Magnetic Moment: A vector quantity that represents the strength and direction of a magnetic source, influenced by the distribution of electrons within an atom or ion.

Coordination Compounds:

Complexes formed by the coordination of metal ions with ligands, which can exhibit varying magnetic properties depending on the arrangement and number of unpaired electrons.