Band Theory of Solids: Electron Conduction & Current

In summary, the discussion focused on the role of electrons in conduction and partially filled valence bands in metals, specifically in relation to their ability to conduct current. It was mentioned that in metals, either the conduction band is partially filled and the valence band is partially empty, or the two bands overlap. The question was raised about the location of the partially filled valence band in a metal. It was clarified that in semi-metals like Bismuth and graphite, there is one band almost filled and one band almost empty, but the terminology of conduction and valence bands can be misleading. It was also suggested that while the electrons in the valence band can move, they do not contribute to current unless there is a
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Do electrons in conduction band are only responsible for current? Don't the electrons in partially filled valence band capable of moving contribute to current?
Material discussed-metals(conductors)
 
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Where is this partially-filled valence band in a metal?

Zz.
 
  • #3
ZapperZ said:
Where is this partially-filled valence band in a metal?

Zz.
In metals either of the two cases exists-
1. Conduction band is partially filled and the valence band is partially empty. OR
2. Conduction and valence band overlap.
 
  • #4
Quotes said:
In metals either of the two cases exists-
1. Conduction band is partially filled and the valence band is partially empty. OR
2. Conduction and valence band overlap.

Show me the band structure where the valence band is partially empty.

Zz.
 
  • #5
ZapperZ said:
Show me the band structure where the valence band is partially empty.

Zz.
 

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  • #6
This references are utterly confusing (what text are you using that has a typo of valence being replaced by "balanced"). The 2nd one, especially, is trying to differentiate between a metal and a semiconductor! We know about unfilled valence band for semiconductor. What I'm asking is for you to show me an example on the band structure of a metal that has a partially empty valence band.

I bet you that what is being described here is the difference between an insulating and a conducting state of a semiconductor! This is not a metal! A semiconductor may be conducting, but it is STILL not a metal! The valence band of a metal doesn't play a role in its charge transport properties. A semiconductor does!

I suggest you look very, VERY carefully at what you are reading and the terminology that you are using.

And please read this thread on why I consider the explanation of "band overlap" is flawed:

https://www.physicsforums.com/threads/how-does-band-structure-lead-to-metals-insulators.839172/

Zz.
 
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In semi-metals like Bismuth and graphite, you encounter the situation that there is one band almost filled and one band almost empty. Personally, I generally would avoid speaking of conduction and valence bands as this termini are clearly missleading.
 
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  • #8
Quotes said:
Do electrons in conduction band are only responsible for current? Don't the electrons in partially filled valence band capable of moving contribute to current?
Material discussed-metals(conductors)
The electrons in valence band move with their corresponding group velocities but they don't conduct any charge because they move in different directions. I think it is possible to have conduction by the electrons in partially filled valence band provided that the symmetry of distribution in the band is broken.
 
  • #9
If this were true, p-doped semiconductors would be isolators, too.
 

1. What is the Band Theory of Solids?

The Band Theory of Solids is a model used to explain how electrons move through a solid material. It states that the electrons in a solid are organized into energy bands, which determine their allowed energy levels and movements within the material.

2. How does the Band Theory explain electron conduction in solids?

The Band Theory explains that in a solid material, there are two types of energy bands: valence bands and conduction bands. The valence band contains electrons that are tightly bound to their respective atoms, while the conduction band contains electrons that are free to move and conduct electricity. When a small amount of energy is applied to the material, some electrons from the valence band can jump to the conduction band, creating a flow of current.

3. What is the role of energy levels in the Band Theory?

The energy levels in the Band Theory determine the position of the bands and the movement of electrons within the material. In a solid, the energy levels are closely packed together, forming bands. The allowed energy levels for electrons in a solid are determined by the atomic structure and bonding of the material.

4. How do impurities affect the Band Theory of Solids?

Impurities in a solid can create energy levels within the energy bands, known as dopants. These dopants can create new energy levels that allow electrons to move more easily through the material, increasing its conductivity. Impurities can also disrupt the regular structure of the material, creating defects that can affect the movement of electrons.

5. How does temperature affect the Band Theory of Solids?

Temperature can affect the Band Theory by increasing the energy of the electrons in the material. As the temperature rises, some electrons in the valence band can gain enough energy to jump to the conduction band, increasing the material's conductivity. However, at very high temperatures, the bands can overlap, making it difficult for electrons to move and decreasing the material's conductivity.

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