Bonding – Color and Magnetic Properties

Introduction 

The strength and direction of magnetism in particular elements are referred to as the magnetic moment of the system. This term is related to the magnetic dipole moment of different elements. Being a vector quantity, the magnetic moment comes with direction and magnitude. For instance, an electron with its intrinsic spin property makes the electron an electric charge in motion. To explain the magnetic behaviors, the concept is divided into three major types – diamagnetism, paramagnetism, and ferromagnetism. The transition metals are known to form magnets as they have unpaired electrons that are magnetic in nature. 

● Transition Elements & Their Magnetic Properties 

With the change in the unpaired and paired electrons, the extent of magnetic properties changes in it. Each element has some form of magnetic property due to the presence of a magnetic field. The origin of the magnetic field is due to the presence of electrons present in the valence shell of an atom. These electrons are known as small current loops that have the power to retain magnetic moments. The magnetic moment of the system arises due to two major electronic motions. 

1. Firstly, when electrons are spinning around an atom’s nucleus. 
2. Secondly, the orbital movement of the electron around its own axis. 

● Properties Of Magnet 

This section focuses on different magnetic properties including definition, properties, and other characteristics of magnets.

1. Diamagnetism 

Due to the absence of unpaired electrons in the atom, the diamagnetic material has little to no magnetic effect. Diamagnetism is effectively explained by Lenz’s law that defines that by curing the presence of an external magnetic field, the diamagnetic materials get induced dipoles. Additionally, the external magnetic field and the dipoles that are induced repel each other. Here are a few properties of diamagnetism/diamagnetic materials. 

• All the electrons in the diamagnetic materials are paired. No unpaired electron is present in the valence shell, which in turn leads to atomic dipole absence. The reason is that the magnetic moment of both the atoms cancels each other. 
• The diamagnetic materials and magnets repel each other when a magnetic field is present around it. 
• When the non-uniform magnetic field is present around the substances, it can lead to the substance transfer from the stronger region to the weaker one. 
• Magnetic susceptibility of diamagnetic materials is low and negative. 
• Relative permeability is relatively lower than unity. 
• Such substances don’t obey Curie law. Meaning they are independent of temperature. 
• The magnetic field in such substances is higher at the poles. Meaning, when suspended from the rod, the substance comes to rest in the perpendicular direction with respect to the magnetic field. 

2. Paramagnetism 

The property of magnets is further divided into paramagnetic substances. Such substances are known to attract when placed in a strong magnetic field. The reason is that such paramagnetic substances have unpaired electrons present in their valence shell. Being in a constant spinning motion, the materials develop a small dipole moment. The development of dipole moments makes them act as small magnets. However, the dipoles developed in such substances are in a random direction. Meaning, they don’t interact with each other, resulting in zero magnetic fields. Here are a few properties of paramagnetic materials. 

• Due to the presence of unpaired electrons in the valence shell, the paramagnetic materials are known to develop dipole moments. 
• In the presence of a non-uniform electric field, these materials move from weaker to stronger regions. 
• Magnetic susceptibility or degree of magnetization in such substances is small and positive. 
• Magnetic permeability is greater than or equal to 1.
• The attraction between paramagnetic materials and electric or magnetic fields is weak. 
• These substances are known to depend on temperature. Meaning, the magnetization of such substances is inversely proportional to temperature. 
• When a paramagnetic material is placed in the magnetic field, the applied field and dipole moments are parallel to each other. 

3. Ferromagnetism 

Even though there are other types of magnetic properties too, ferromagnetism is one of the most powerful among them. Even if there is no external magnetic field present, a spontaneous net magnetization is developed in such substances. Furthermore, when such substances are placed in the magnetic field, the substance gets strongly magnetized in the direction of the field. When the external field is removed, the substance tends to remain in a magnetization state for a certain time period. Some properties of ferromagnetic substances that make them different from other types of substances are: 

• The atomic dipoles are developed in the same direction as the applied external magnetic field. 
• The magnetic dipole moment is large and oriented. 
• Ferromagnetic substances have high and positive magnetic susceptibility. 
• The magnetic flux density is positive and high, with thick magnetic lines present inside it. 
• One of the main things that differentiate ferromagnetic substances from others is their characteristic of losing power. When the material gets liquified at a high temperature, it results in a loss of characteristics.
• In such substances, the field is strong at poles as compared to the other places. 

Color Of The Transition Elements 

To explain the concept of color in the transition elements, make sure you pay a keen focus at this point. When the energy is absorbed by the valence electrons, they get excited from low lying level to high lying level. The low lying level in the molecule is known as Highest Occupied Molecular Orbital (HOMO), whereas the high lying level in the molecule is known as Lowest Unoccupied Molecular Orbital (LUMO). When such electron transition takes place, the light is absorbed, and the result shown is coloured. The energy difference between the two orbitals is directly proportional to the wavelength of light that is absorbed. 

Conclusion 

Transition metals are known to possess colors that are shown when electrons shift from one level to another. On the other hand, non-transition ions are colorless. When light is passed or reflected, mixed wavelengths are absorbed. And the remaining light assumes the complementary color. Meaning, when one color in the spectrum is absorbed, an opposite or complementary color is observed. For instance, when the material absorbs violet light, the yellow color is observed.