Do semiconductors have to have a full valence band?

[nonequilibrium]

Hello,

In my book it says that semiconductors have a full valence band and a fermi energy somewhere in between that valence band and the conduction band. But its two examples of semiconductors, crystals of Silicon or Germanium, have a $$3s^2 3p^2$$ resp. $$4s^2 4p^2$$ outer shell, so surely they can't result in a full valence band?

Thank you.

 

[Mapes]

A valence shell is different from a valence band. It's possible for atoms with partially empty valence shells to have full valence bands because the energy levels of the electrons widen into bands and can split when the atoms are brought close together, as is the case with a solid.

 

[nonequilibrium]

Hm, I thought that each azimuthal quantum number $$l$$ corresponded to one valence band, that is what my book is implying anyway, but I suppose that's wrong then.

Thank you.

 

[zhanghe]

well :) A single atom is one thing, and a group of closed atoms (material) is another thing.

 

[nonequilibrium]

wow, that's the worst explanation I've ever had about anything