Electron Band Energy in Solids

Anything that has mass and occupies space is called matter.

The matter is mainly of three types i.e. Solid, Liquid and Gas.

Solids have a definite shape and hard to compress.

The particles in solids are closely packed together.

While liquid and gas do not have any fixed shape and can flow.

In a liquids and gases, the particles are less densely packed as compared to solids.

In this story, we will learn about the solids in detail.

Let's discuss the electron energies in solids.

On the basis of conductivity, solids can be categorized into $3$ types i.e. Conductor, Insulator, and Semiconductors.

The conductors have very less resistivity or high conductivity.

While Insulators have very high resistivity.

And Semiconductors have a resistivity or conductivity between conductors and insulators.

We can differentiate the Insulators, Conductors, and Semi-Conductors by using Band theory too.

According to the Bohr atomic model, the energy of the electron is decided by the orbit in which it revolves.

But, when the atoms come together to form a solid, they are so close to each other as they can even overlap.

These different energy levels with continuous energy variation formed energy bands.

The energy band which includes the energy levels of the valence electrons is called the valence band.

And the energy band above the valence band is called the conduction band.

The gap between the top of the valence band and bottom of the conduction band is called the energy band gap.

Now, depending on the energy band gap is zero, large or small, the solids can be classified as solid, insulator or semiconductor.

In metals either there is an energy gap between the completely filled valence band and conduction band.

Or the Conduction band and valence band partially overlap each other.

While in Insulators the energy gap between the Valence band and the Conduction band is greater than $3eV$.

And in the Semiconductors energy gap is small ($<3eV$).

Since, the gap is small, some electrons acquire enough energy even at room temperature and enter the conduction band.

These electrons can move in the conduction band and increase the conductivity of the solid.

Revision

On the basis of conductivity, solids are categorized into three types i.e. Conductor, Insulator, and Semiconductors.

The Conduction band and valence band partially overlap each other in Metals.

While in Insulators the energy bandgap is greater than $3eV$.

And in the Semiconductors energy gap is small ($<3eV$).

The End