Valence Band and Conduction Band

Valence band and conduction band are significant topics as these determine the conductivity of a given material. These can be seen as two different types of energy levels that are kept apart by the same amount of energy. It will help us to differentiate between the two and find out their relevance concerning the band theory of solids.

In the discussion below, we will go through the two concepts in detail and look at their various aspects. We will also look at some of the most prominent differences between the two concepts and how they are represented graphically when required.

Meaning of Conduction Band

Any band of electron orbitals where the electrons can switch from the valence band upon getting energy is termed the conduction band. Whenever these electrons are in their orbitals, it demonstrates that the given material has sufficient electrical conductivity. This shift made by the electrons enables the electric current to flow through the material. In such a situation, the valence band becomes an electron orbital situated far from the spot where the electrons are typically involved. The conduction band and valence band seem to overlap each other in the case of metals which enable the electron to frequently shift between the two groups, which gives the material enough conductivity.

Meaning of Valence Band

Valence band refers to the band of electron orbitals with the capability to jump out of the conduction band upon getting excited. It is undoubtedly the outermost electron orbital of any given atom of a specific object occupied by electrons, which is closely associated with the valence band.

Similar to the concept of the conduction band, the bandgap is present as the annual difference between the lowest occupied energy state and the highest one. The presence of a large band gap implies that the valence electrons will need a lot of energy to get excited in the conduction band. On the other hand, electrons can easily switch between two given bands when the conduction band and the valence band overlap, implying that the material possesses highly conductive properties. 

In addition to this, insulators usually have a large band gap employing that electrons would need a large amount of energy to move out of the valence band to give rise to electronic current. On the other hand, in the case of semiconductors, there is a relatively smaller bandgap enabling more fractions of valence electrons belonging to the material to shift to the conduction band considering the given amount of energy. 

This trait facilitates a property of conductivity between insulators and conductors, which is a significant reason why there is no resulting short circuit in the case of these materials. The existing band gap also facilitates semiconductors to convert one form of energy to another and release the light same as LED when paired with a certain category of diodes. 

Both phenomena depend on the energy that is released or absorbed by electrons showing movement between valence bands and conduction. Some relevant valence band examples include silicon atoms consisting of 4 electrons in the valence band and phosphorus with 5 such electrons. 

Difference between Valence Band And Conduction Band

Some of the notable differences between the valence band and conduction band are given as follows:

• Placement on the graph 

When these bands are presented in the form of a graph, the conduction band is located above the Fermi level. On the other hand, the valence band is located below the specific energy level.

• Abbreviation used

The valence band is represented by VB, while the conduction band is represented by CB. 

• Impact of external excitement

In the case of valence bands, they move out while they reach the conduction band in the other case.

• Influence of the presence of electrons

Electrons present in the valence band are partially or fully filled. However, in the case of conduction bands, electrons are either partially filled or empty.

• Energy state

The state of energy in valence bands is comparatively lower than the conduction band, which has a relatively higher level of energy state. 

• Electron density

Electron density is comparatively higher in the case of the valence band than in the conduction band.

Conclusion 

From the above discussion, it can be concluded that the valence band and the conduction band depend on a lot of factors. In a nutshell, we can also conclude that the valence band and the conduction band are two significant categories of energy levels. These are differentiated by a certain amount of energy required to keep the electrons moving from one orbit to another. There are also several differences between the two concepts as they differ on various grounds. 

The basic difference between the valence band and conduction band is that the former consists of electrons placed in the outermost shell of the atom. On the other hand, the latter is composed of free electrons that participate in the process of conduction. 

Material such as insulators, conductors, and semiconductors also differ based on several grounds in terms of the energy present between the conduction band and the valence band.