Energy Bands and Molecular Orbitals

[ABhattacharya]

Hello, a newbie here. I need to understand the relationship between MO and Energy Bands.

Although i have searched and researched about this topic in Google, but i am yet to understand this part clearly.

It is said that Energy Bands occur as the number of MO increase due to the various atoms that are interlinked in a crystal structure.

But i can't help but wonder.
While K has its σ state fully filled and its σ* state empty, and yet behaves as a conductor
But Si has ∏px and ∏py states partially filled which means when bands form, Si should have some bands which are partially filled and hence should be good conductors while Na should behave more of a semiconductor way... but it is just the opposite. Why?

 

[DrDu]

The diagram you show seems to be for diatomic molecules while the band structure refers to infinitely large crystals. Why do you think the two are comparable?

 

[ABhattacharya]

The diagram you show seems to be for diatomic molecules while the band structure refers to infinitely large crystals. Why do you think the two are comparable?

Then what should i do to get a clearer picture of the MO and Energy Band conduction??

 

[DrDu]

Try to understand Bloch's theorem.
http://en.wikipedia.org/wiki/Bloch_wave
Then do some model calculations for one dimensional systems, like e.g. a chain of hydrogen or helium atoms.