Valance and conduction band in solid.

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Discussion Overview

The discussion revolves around the formation of valence and conduction bands in solids, particularly in the context of atomic interactions and energy levels. Participants explore the relationship between atomic orbitals and the resulting energy bands, addressing both conceptual and technical aspects.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant proposes that in a hypothetical lithium molecule, the 1S shell splits into multiple 1S shells, suggesting that the energy levels formed by these shells could be considered the valence band, while those from the 2S shell could represent the conduction band.
  • Another participant argues that the concept of valence and conduction bands is more complex than a simple atomic model, noting that the wave functions of combined atoms do not retain the same nomenclature as individual atomic orbitals.
  • A different participant expresses confusion regarding the relationship between the valence band and the valence shell of an atom, referencing textbooks that correlate these concepts and questioning the origin of the conduction band electrons.
  • One participant acknowledges the previous explanation but mentions that their chemistry class taught a simpler view of energy bands, suggesting that some chemists may still consider the atomic states as relevant to the conduction band formation.
  • A later reply questions the logic of considering all atomic nuclei as a single point in relation to the proximity of the valence and conduction bands to the nuclei.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of using atomic models to explain band formation, with some supporting a simplified approach while others emphasize the complexities involved. No consensus is reached on the validity of the initial propositions regarding band formation.

Contextual Notes

Participants highlight limitations in the understanding of energy band formation, including the dependence on definitions and the complexity of quantum mechanical interactions that may not align with classical interpretations.

PhysicsBegner
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Hi, I have a very basic question on formation of valance and conduction band. It is said that conduction band is above the valance band.

So In a hypothetical lithium molecule formation(for example purpose) : If 100 Lithium atoms combine together, then 1S shell is split into 100 1S shells (one 1S shell and 99 shells closer to it) with 2 electrons each. And 2S shell smiliarly splitted into 100 shells.

In the above example can we say band of energy levesl formed by 1s shell as valance and band of energy levels fromed by 2s energy levels as conduction.

Please correct me.
 
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I would say the issue is more complicated than this simple treatment. The valence and conduction bands are merely names just to simplify the complicated wave function that takes place due to the combination of the atoms in the space. The 1S "orbit" is not called 1S anymore in quantum mechanics when it's a combination of more than 1 atom, because it's not simply the superposition of the two quantum states. The names become more complicated.

Generally, in solid state physics, we are not concerned at all about individual atoms. I don't know why you're asking this question, maybe you just want to feel more understanding for the matter, but this isn't the right way I guess.

Hope this gave you the picture.
 
Last edited:
Thank you. I wanted to ask this question because I had a doubt of whether the valance band woluld be formed with electrons in the valance shell of atom. Because some textbooks in electronics co-rellates valance band and valance shell in an atom. And I was wondering then from which part of electrons the conduction band would be formed.
 
I don't disagree with what TheDestroyer said, but I just want to say that I took a chemistry class in which they explained energy bands in exactly the way you described it, so I think some chemists do think of it this way. Even if it's no longer meaningful to talk about 2s states, orbitals, or whatever, I think these are indeed the states that went into forming the conduction band.
 
Thank you, If this classical way of explaining band formation in solid is correct. Could we logically think that nucleous of all atoms are at one point; since we say valance band is nearer to atom's nucleous and conduction ban is far away from nulceous?
 

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