# Thread: Band gaps

1. Do materials classified as conductors have no band gap, or only a negligible one?

If they have no band gap, what does that mean? That no space exists between the orbitals of one atom and the other?

2. Originally Posted by nietzscheswoman
Do materials classified as conductors have no band gap, or only a negligible one?

If they have no band gap, what does that mean? That no space exists between the orbitals of one atom and the other?
Conductors either have very small band gaps or none, because the valence and conduction bands overlap

3. When the valence and conduction band overlap, what does that mean in terms of how the atoms are oriented? They're so close together that it looks like one big atom? Can the atoms be separated in a conductor?

4. Originally Posted by nietzscheswoman
When the valence and conduction band overlap, what does that mean in terms of how the atoms are oriented? They're so close together that it looks like one big atom? Can the atoms be separated in a conductor?
The nucleii are definitely separated, the electrons form a continuous band (the conduction band). You can no longer tell which electron belongs to which atom.

5. And when the valence band and conduction band overlap completely, 0 energy is required to "span the gap", right?

6. Originally Posted by nietzscheswoman
And when the valence band and conduction band overlap completely, 0 energy is required to "span the gap", right?
Right

7. How can a material require 0 energy to conduct? Wouldn't it immediately burn up? Energy is everywhere. It will conduct anything. And then...disappear. No?

8. Originally Posted by nietzscheswoman
How can a material require 0 energy to conduct? Wouldn't it immediately burn up? Energy is everywhere. It will conduct anything. And then...disappear. No?
The conduction happens only if a voltage potential (i.e. energy) is APPLIED EXTERNALLY.

9. But what does it mean to conduct anything if there is no gap to bridge?

I'm picturing two atoms side by side with no band gap between orbitals. A voltage potential is applied externally. It doesn't conduct. How can it "conduct" between atom 1 and atom 2 if there is no distance between them?

10. Originally Posted by nietzscheswoman
But what does it mean to conduct anything if there is no gap to bridge?

I'm picturing two atoms side by side with no band gap between orbitals. A voltage potential is applied externally. It doesn't conduct. How can it "conduct" between atom 1 and atom 2 if there is no distance between them?
The electrons in metals are free to move, basically metals do not have valence bands, they only have conduction bands.

11. The electrons get rearranged within the same orbital?

12. My understanding of a band gap is the distance between discrete orbitals of two atoms. I just thought every solid material had band gaps since orbitals are always discrete.

13. Originally Posted by nietzscheswoman
The electrons get rearranged within the same orbital?
More like the electron orbitals of the atoms get "blended together" to the extent that you no longer have electrons "belonging" to a certain atom.

14. Originally Posted by AndrewC
More like the electron orbitals of the atoms get "blended together" to the extent that you no longer have electrons "belonging" to a certain atom.
For details, see here.

15. Is the bond between electrons in metals a covalent bond?

16. Do only solid-state material have band gaps?

17. Originally Posted by nietzscheswoman
Do only solid-state material have band gaps?
Yes

18. Originally Posted by nietzscheswoman
Is the bond between electrons in metals a covalent bond?
No

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