Energy bands in solids

Thread Starter

Legend killer

Joined Jan 24, 2010
10
Hello everyone,
I am trying to learn about the energy bands which forms when atoms interact with each other. However I am unable to actually visualize the whole picture. As per my understanding I have created a diagram which I think might be correct way of visualizing the whole picture. Can anyone please tell me whether I am correct or wrong. I have attached the image with this post
 

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studiot

Joined Nov 9, 2007
4,998
It's very hard to tell if you are on the right lines or not from your diagram alone without any explanation of your thinking.

So I will make the following comments.

I don't know what the curved blue lines with the electrons are meant to represent?

You need to be aware that there is only one electron at any energy level per atom.
(Or two per level if you count the Pauli pairing)

It is only the bonding or valence electrons that take part in fromation of molecular orbitals that lead to the energy bands.
The main core of electrons remain unaffected.
Note it is often said that these bonding electrons are the outmost electrons but that is not always the case.

With only two atoms participating you only get a well defined molecular orbital. When you get a vast array of atoms participating these molecular obitals smear out to form the energy bands.

Is your ultimate goal to use energy bands to understand insulators, conductors and semiconductors and perhaps tunneling?
 
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amilton542

Joined Nov 13, 2010
497
Hello everyone,
I am trying to learn about the energy bands which forms when atoms interact with each other. However I am unable to actually visualize the whole picture. As per my understanding I have created a diagram which I think might be correct way of visualizing the whole picture. Can anyone please tell me whether I am correct or wrong. I have attached the image with this post
I'm at odds just how two atoms could interact when, by way of your diagram, they're an infinite distance d apart.

Being well versed with the periodic table and how solids, such as alloys, are formed is rudimentary ground that needs to be covered.

By the way, the energy levels associated with the orbits of electrons is quantem mechanics. This stuff is not easy. Some engineers will bite, others will not.
 

Thread Starter

Legend killer

Joined Jan 24, 2010
10
Hello studiot and amilton542
Thanks for your replies
In the diagram( two atoms shown on top), i was indicating that the electrons in atoms have discrete energy levels when they are isolated from each other. The blue lines indicates orbits which i have not drawn as complete circles and i have also indicated y-axis as energy which indicates that energy of electrons increases as distance from nucleus increases. Next (atoms shown in bottom), i have drawn four lines instead of one because now there will not be single discrete energy level, instead there will be four closely spaced energy levels for the four electrons (as per my understanding).
Am i correct or wrong in my understanding?
 

Papabravo

Joined Feb 24, 2006
17,030
Atoms in isolation have plenty of discrete energy levels without regard to any other atoms. An atom can absorb a photon and be boosted to a higher level by absorbing the photon energy. When the electron drops back to a lower state it emits a photon with a well defined wavelength based on the amount of energy given up.

What happens when atoms are in proximity is that the most energetic electrons are in the so-called valence band. It is the electrons in this valance band that have the most influence on the chemical and electrical properties. There are also electrons that are far enough away from any nucleus to be considered essentially "free" electrons or "conduction" electrons. In semiconductors there is an energy gap (aka "band gap") between the valence electrons and the conduction electrons.

In your picture there is a suggestion that proximity creates new discrete energy levels where none existed before. This is not the case. Any given electron with some non-zero probability can have any combination of quantum numbers that are available. For example, a Hydrogen atom has a single 1s electron. The 1s refers to the lowest energy level an electron of a hydrogen atom can have. If it absorbs a photon, raising its energy level, it might become 4p electron for a short time and then return to the 1s state after one or more quantum jumps.

These links might help
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/quantum.html
http://en.wikipedia.org/wiki/Band_gap
http://en.wikipedia.org/wiki/Pauli_exclusion_principle
 
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