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Author Topic: Does the electromotive force cause the electron band gap to change?  (Read 872 times)

Offline Nicholas Lee

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Somebody told me on this chemistry forum, "By applying an electric field you can move the energy levels of a substance up and down, but in most cases they all move together, preserving the distance of the band gap. There are some materials (mostly molecular, as far as I know) for which the energy levels move slightly differently as the electric field is applied--causing a change in the difference between energy levels. It is very uncommon for this to be a strong effect, and it has to do with differential coupling between the orbitals involved."
Can you explain this more simply, to show how it effects the band gap.
I am grateful for your help anything helps even a few words.
« Last Edit: 17/07/2016 23:13:21 by chris »


 

Offline chiralSPO

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see attached
 
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Offline Nicholas Lee

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Form molecules of glass.
When atoms, come together to form molecules of glass, transparent liquid, do the electrons reside in higher shell level 1, or 2 when the?
atoms have formed molecules to become glass, in order for the electrons energy level to change.
Like for example glass is made from silicon, sodium, and calcium, all these elements absorb light, but when these elements came together to form glass, did the electrons in THEIR ground state move to higher shell levels, when they come together to form covalent bonds to become glass.
Or another way to look at it is, is the electron in the ground state in silicon, sodium, and calcium, in the same place as the electron when it is in the ground state in glass.
Has the electron moved to a higher shell level, while it is still in the ground state in glass.Is this why light does not absorb, but ultra violet waves do, because the electron is in the ground state but in a shell level, that would be either 1,2or 3 in opaque matter, or is this wrong, and its just the energy level of the electron that has changed, it has not moved to any different shell level.
I am grateful for your help, anything helps even a few words. :D
 

Offline Nicholas Lee

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Also like in glass, light does not get absorbed by the electron but ultra violet does.
I am thinking the further away the electron is, then it only absorbs electromagnetic waves on the high end of the spectrum, like ultra violet, X-rays, and Gamma.
But is this wrong, like the electron eV requirment does change when it is far away from nucleus in a higher shell level.
But I guess it can absorb any EM wave while in the ground state is this correct.
Also is it known to science why the electrons energy levels (eV requirment to be absorbed by EM waves) change when atoms come together to form molecules, like in glass, and transparent liquids especially, and also when the electron is away from its nucleus.
The electron speeds up when its away from the nucleus but nothing I have read explains why the eV changes.
Its like its a mystery, does science have a answer.
I am grateful for your help, anything helps even a few words. :D
« Last Edit: 13/06/2016 08:06:57 by Timemachine2 »
 

Offline evan_au

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Quote from: Timemachine2
I am thinking the further away the electron is, then it only absorbs electromagnetic waves on the high end of the spectrum, like ultra violet, X-rays, and Gamma.
I think the trend is the opposite.

Outer electrons tend to be the easiest to lose, especially if this is the only electron in the outer shell - metals like Sodium lose their outer electron fairly easily in chemical reactions. Have a look at the photoelectric effect. (But be aware that light striking a metal tends to be reflected away, rather than being absorbed.)
https://en.wikipedia.org/wiki/Photoelectric_effect#Emission_mechanism

Inner electrons (close to the +ve nucleus) have a strong attraction to the nucleus. It takes a large amount of energy for a photon to knock them out. In an X-Ray machine, a beam of electrons knocks out an inner electron from a large atom like tungsten; when the remaining electrons fall into this "hole", they emit X-Rays.
https://en.wikipedia.org/wiki/X-ray#Production_by_electrons

Gamma Rays have so much energy that they can't really be produced by the attraction between the electrons and protons within a single atom. They are mostly produced by nuclear rearrangements of the protons and neutrons in a nucleus.
Gamma rays can also be produced by large modern high-energy particle accelerators - and even in natural particle accelerators like the upper atmosphere above thunderstorms.
See: https://en.wikipedia.org/wiki/Gamma_ray#General_characteristics
 
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Offline chiralSPO

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The energy levels definitely change when atoms rearrange (when chemical reactions occur). You might be interested to read up on some of this instead of asking all of these questions.

These will get you started:
https://en.wikipedia.org/wiki/Molecular_orbital_theory
https://en.wikipedia.org/wiki/Molecular_orbital_diagram
https://en.wikipedia.org/wiki/Electronic_band_structure
 
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Offline Nicholas Lee

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Does electron give any sign it has changed energy levels.
« Reply #6 on: 14/06/2016 08:36:07 »
Does anything happen to the electron, as it changes energy levels, does its mass increase, or decrease, or velocity speed up, or slow down.?
The electron will speed up when its away from the nucleus, when its in a higher shell like shell level 3.
But is there anything like a visible sign, or indication like in mass, speed, weight, or becomes less negative, pr positive if possible, just any indication that the electron has changed energy levels, (energy requirement to EM waves to absorb, and emission).
The electron is a mysterious particle that seems to give no indication of its change in energy requirment, in electron volts, as atoms come together to make covelent bonds to form molecules
I am grateful for your help, anything helps even a few words. :D
 

Offline evan_au

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Re: Does electron give any sign it has changed energy levels.
« Reply #7 on: 14/06/2016 10:47:39 »
An example of calculating the energy released when chemical bonds form can be read here:
https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation#Calculation

However, what this does to the energy levels inside the material is a much more complex question.
 
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Offline chiralSPO

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Re: Does electron give any sign it has changed energy levels.
« Reply #8 on: 14/06/2016 14:28:35 »
Does anything happen to the electron, as it changes energy levels, does its mass increase, or decrease, or velocity speed up, or slow down.?
The electron will speed up when its away from the nucleus, when its in a higher shell like shell level 3.
But is there anything like a visible sign, or indication like in mass, speed, weight, or becomes less negative, pr positive if possible, just any indication that the electron has changed energy levels, (energy requirement to EM waves to absorb, and emission).
The electron is a mysterious particle that seems to give no indication of its change in energy requirment, in electron volts, as atoms come together to make covelent bonds to form molecules
I am grateful for your help, anything helps even a few words. :D

An electron is an electron. It won't ever change its charge or its proper mass or the magnitude of its spin. None of the intrinsic properties of the electron changes. Really, one must consider the whole system as changing when a chemical reaction or excitation occurs, but none of the components change. Somewhat like assembling a car from its components: the wheels and axles are still wheels and axles, but now they are part of a car; and when the car starts driving, they are still wheels and axles, they are just moving...
 
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Re: Does electron give any sign it has changed energy levels.
« Reply #8 on: 14/06/2016 14:28:35 »

 

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