Valance and conduction band in solid.

[PhysicsBegner]

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.

[TheDestroyer]

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.

[PhysicsBegner]

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 text books 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.

[johng23]

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 in to forming the conduction band.

[PhysicsBegner]

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?