Would you please explain this statement please...........

[eis3nheim]

As the atoms of a material are brought closer together to form the crystal lattice structure, there is an interaction between atoms, which will result in the electrons of a particular shell of an atom having slightly different energy levels from electrons in the same orbit of an adjoining atom. The result is an expansion of the fixed, discrete energy levels of the valence electrons. In other words, the valence electrons in a silicon material can have varying
energy levels as long as they fall within the band .

[swansont]

It's related to the Pauli exclusion principle. The electrons can't occupy the same state, so there must be an energy difference between them. That works if there is a band of energy states they can occupy, rather than one of a single value.

[studiot]

To understand this first you need the Pauli Exclusion Principle.

 

This states (for this purpose) thjat no two electrons can have the same set of quantum numbers.

 

 

Now the usual quantum solution that we use to describe an atom is for an 'isolated' atom.

That is it specifies a set of quantum numbers for an single atom in isolation.

 

But if we have two such atoms the set will be the same.

So what happens if we join them together?

 

Well each nucleus influences the other's bonding electons (that is what bonding means) and the electrons directly involved in the joining enter what are known as molecular orbitals with enough quantum numbers to hold them all.

 

Move on to a full crystal which is also called a periodic structure and you find 'super molecular orbitals' which can hold all the input electrons.

Obviously in order to obey the Pauli Principle the super molecular orbital must 'split' into many closely spaced (sub)orbitals to accomodate all its electrons.

 

Does this help?

[eis3nheim]

It's related to the Pauli exclusion principle. The electrons can't occupy the same state, so there must be an energy difference between them. That works if there is a band of energy states they can occupy, rather than one of a single value.

Would you explain it please

 

To understand this first you need the Pauli Exclusion Principle.

 

This states (for this purpose) thjat no two electrons can have the same set of quantum numbers.

 

 

Now the usual quantum solution that we use to describe an atom is for an 'isolated' atom.

That is it specifies a set of quantum numbers for an single atom in isolation.

 

But if we have two such atoms the set will be the same.

So what happens if we join them together?

 

Well each nucleus influences the other's bonding electons (that is what bonding means) and the electrons directly involved in the joining enter what are known as molecular orbitals with enough quantum numbers to hold them all.

 

Move on to a full crystal which is also called a periodic structure and you find 'super molecular orbitals' which can hold all the input electrons.

Obviously in order to obey the Pauli Principle the super molecular orbital must 'split' into many closely spaced (sub)orbitals to accomodate all its electrons.

 

Does this help?

But how that result in the expansion of the energy level ?

 

[swansont]

Do you know what the Pauli exclusion principle is?

[eis3nheim]

Do you know what the Pauli exclusion principle is?

No.

Would you explain it.

 

Edited March 23, 2015 by eis3nheim

[studiot]

It would be helpful if you can tell us whether you are an studying electrical engineering, physics or chemistry and if you have heard of Fermi?

[eis3nheim]

It would be helpful if you can tell us whether you are an studying electrical engineering, physics or chemistry and if you have heard of Fermi?

Iam studing electrical engineering, and this statement is about the semiconductors.

 

[Mordred]

Ok lets use electrons and any atom.

 

You have 4 quantum numbers,

Principle quantum number=n

Azimuthal quantum number=L

Magnetic quantum number=[latex]m_l[/latex]

Spin quantum number.[latex]m_s[/latex].

 

The principle quantum number is covered here

http://en.m.wikipedia.org/wiki/Principal_quantum_number

Azimuthal here

http://en.m.wikipedia.org/wiki/Azimuthal_quantum_number

Magnetic

 

http://en.m.wikipedia.org/wiki/Magnetic_quantum_number

Spin here

http://en.m.wikipedia.org/wiki/Spin_quantum_number

 

bosons have integer spins,1,2,3 etc

Fermions have 1/2 integar spins.

 

[latex]n+\frac{1}{2}[/latex]

 

n is an integer value.

 

The Pauli exclusion applies only to fermions (electrons, protons neutrons etc.) Sample bosons is the photon, W and Z boson,mesons etc.

 

"The Pauli exclusion principle is the quantum mechanical principle that says that two identical fermions (particles with half-integer spin) cannot occupy the same quantum state simultaneously. In the case of electrons, it can be stated as follows: it is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers (n, ℓ, mℓ and ms)"

 

http://en.m.wikipedia.org/wiki/Pauli_exclusion_principle

 

Here is an article with some practice exercises.

 

http://en.m.wikibooks.org/wiki/High_School_Chemistry/Pauli_Exclusion_Principle

Edited March 24, 2015 by Mordred