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Author Topic: Why aren't electrons in the nucleus?  (Read 10384 times)

Offline Bill S

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Re: Why aren't electrons in the nucleus?
« Reply #25 on: 10/06/2015 20:09:18 »
Wasn't the electron a bit of a family thing with the Thompsons?  If I remember rightly JJ identified the electron as a particle, and his son discovered its wave nature.
 

Offline PmbPhy

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Re: Why aren't electrons in the nucleus?
« Reply #26 on: 11/06/2015 05:11:39 »
Quote from: Bill S
Wasn't the electron a bit of a family thing with the Thompsons?  If I remember rightly JJ identified the electron as a particle, and his son discovered its wave nature.
Yep. Your memory is spot on (although you spelled his last name wrong which made it difficult for me to do a search). Good for you my friend! :)  His son's name is George Paget Thomson

http://en.wikipedia.org/wiki/George_Paget_Thomson
 

Offline jerrygg38

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Re: Why aren't electrons in the nucleus?
« Reply #27 on: 12/06/2015 10:00:18 »
   Bohr produced a physical model of the hydrogen atom which involved simple algebraic equations. QM defined the hydrogen atom using very complex math. Is the universe a simple place or a more complex place? If we add the Einsteinian energy to the Bohr model we find that the neutrino is the amount of energy for the electron to reach a speed of 0.9186C as it reaches the proton radius. This can only happen if we compress the hydrogen atom to the neutron. That is a simple explanation. QM may be a mathematical solution but does it really tell us how things work? In effect it is another model which tells us some things but does not tell us everything. It fails to provide us with an understanding of gravity and dark energy. Therefore it is only a particular theory which is useful in describing the workings of particles and sub-particles as we bash them up. Since it is hard to understand by the average person, its value in explaining the universe is quite limited.
 

Online evan_au

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Re: Why aren't electrons in the nucleus?
« Reply #28 on: 12/06/2015 13:43:59 »
Quote from: jerrygg38
the neutrino is the amount of energy...
I'm afraid I don't understand this.
Do you mean the rest mass of the neutrino (there are 3 kinds of neutrino known)? This has proven very difficult to measure, but is thought to be somewhere around 0.1eV (and the different kinds of neutrino may differ by a few orders of magnitude).

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energy for the electron to reach a speed of 0.9186C as it reaches the proton radius
  • If you imagine an electron as a negative point charge, being attracted from an initially stationary position towards the proton in the centre of a hydrogen atom, it could well reach relativistic speeds.
  • Or if you imagine an electron as a negative point charge, being attracted towards the proton in the centre of a hydrogen atom, it would need to reach relativistic speeds to stay in a circular orbit. 

But an electron is not a point charge, nor does it take on a circular or elliptical orbit around the nucleus. The electron fills a 3-dimensional orbital around the nucleus of an atom.
The QM description of an atom describes the orientation of atomic bonds in 3-dimensional space. It also explains the shape of the periodic table. This cannot be matched by a "Solar System" model of the atom.

So QM is more complex, but it also gives better predictions. At this point in time, the Solar System model of the atom is mostly useful as an introduction to the structure of the atom, but it should never be presented as a definitive model!

If (like me), you can't solve Schroedinger's equation, then we must accept the answers from those who have used powerful computers to model the structure of complex atoms in detail. (And it does take relativistic effects into account.)

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It fails to provide us with an understanding of gravity and dark energy.
At this point in time, there is no proven explanation for Dark Matter, let alone integrating gravity with the subatomic world. So that is no reason to prefer one theory over another.

Instead, you should choose a theory to use based on the accuracy you require from its predictions, and your ability to manipulate the theory to produce answers of the required accuracy.

But why "reinvent the wheel"? You could just look up a textbook prepared by someone else which already has tested answers based on physical measurements and/or theoretical predictions.
 

Offline PmbPhy

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Re: Why aren't electrons in the nucleus?
« Reply #29 on: 12/06/2015 18:21:13 »
Quote from: jerrygg38
   Bohr produced a physical model of the hydrogen atom which involved simple algebraic equations. QM defined the hydrogen atom using very complex math.
You're confusing the terms model and define. QM models the hydrogen atom using partial differential equations.

Quote from: jerrygg38
Is the universe a simple place or a more complex place? If we add the Einsteinian energy to the Bohr model we find that the neutrino is the amount of energy for the electron to reach a speed of 0.9186C as it reaches the proton radius.
What do you mean by "Einsteinian energy" and what does it have to do with the hydrogen atom. The hydrogen atom is modeled using non-relativistic QM. And by the way, the neutrino has nothing to do with the hydrogen atom. And the term "speed" doesn't apply to electrons in an atom. The concepts of speed and velocity are foreign to QM.

Quote from: jerrygg38
This can only happen if we compress the hydrogen atom to the neutron.
I can't imagine where you got this notion from? What are you claiming happens? I.e. what is the "this" that can only happen as you suggest?

Quote from: jerrygg38
QM may be a mathematical solution but does it really tell us how things work?
That's incorrect. QM can tell you everything that can be known about how things work. It's not merely a mathematical solution. Layman seem to invariably confuse the math of physics with physical reality. As is well-known to all physicists, math is the language of physics. That means that we describe everything that can and does happen in nature with math, at least in principle.

Quote from: jerrygg38
It fails to provide us with an understanding of gravity and dark energy. Therefore it is only a particular theory which is useful in describing the workings of particles and sub-particles as we bash them up.
That's not a failure of quantum mechanics. It's merely out of its domain of applicability.
 

Offline PmbPhy

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Re: Why aren't electrons in the nucleus?
« Reply #30 on: 12/06/2015 18:32:37 »
Quote from: evan_au
But an electron is not a point charge, ...
Physicists assume that the electron is a point charge. There is every reason to assume that it is and no reason to assume that it isn't. See:
https://en.wikipedia.org/wiki/Electron
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The electron has no known substructure.[1][74] and it is assumed to be a point particle with a point charge and no spatial extent.

See also: http://www.fnal.gov/pub/today/archive/archive_2013/today13-02-15_NutshellReadMore.html
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The quarks, leptons and bosons of the Standard Model are point-like particles.
...
Letís start with the easiest point-like particle we know, the electron... To begin with, since it has zero size, you can never actually see the electron itself.
...
 

Offline lunar7

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Re: Why aren't electrons in the nucleus?
« Reply #31 on: 20/06/2015 15:49:49 »
In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
The electron does not spiral into the nucleus because it is a wave.
One experiment that I have performed on numerous occasions is observing standing waves on a string. Attach a one metre string to a mass and feed this over a pulley attached to a bench so the mass dangles over the bench. The other end of the string is attached to an oscillator which is connected to a signal generator. The string is now horizontal and quite taut. The frequency is varied till the string vibrates in its fundamental mode (the simplest standing wave). This could refer to an electron in the ground state. Now if the frequency is increased then the standing wave disappears and eventually a new standing wave is formed at a particular frequency called the second harmonic. This can represent the electron in the first excited state, above the ground state. This experiment is beautiful because now the students can be informed that the electron cannot exist between the energy levels, as no standing wave formed. Also, the exact frequency was required to move from the first harmonic to the second,  I.e. the need for the correct photon energy between energy levels.
 

Offline jeffreyH

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Re: Why aren't electrons in the nucleus?
« Reply #32 on: 20/06/2015 17:33:18 »
In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
The electron does not spiral into the nucleus because it is a wave.
One experiment that I have performed on numerous occasions is observing standing waves on a string. Attach a one metre string to a mass and feed this over a pulley attached to a bench so the mass dangles over the bench. The other end of the string is attached to an oscillator which is connected to a signal generator. The string is now horizontal and quite taut. The frequency is varied till the string vibrates in its fundamental mode (the simplest standing wave). This could refer to an electron in the ground state. Now if the frequency is increased then the standing wave disappears and eventually a new standing wave is formed at a particular frequency called the second harmonic. This can represent the electron in the first excited state, above the ground state. This experiment is beautiful because now the students can be informed that the electron cannot exist between the energy levels, as no standing wave formed. Also, the exact frequency was required to move from the first harmonic to the second,  I.e. the need for the correct photon energy between energy levels.

Very neat explanation. This kind of demonstration goes a long way towards fostering understanding where mathematics may frustrate it.
 

Offline PmbPhy

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Re: Why aren't electrons in the nucleus?
« Reply #33 on: 20/06/2015 17:34:27 »
Quote from: lunar7
In the first instance, the electron should not be treated as a particle but as a wave that is orbiting the nucleus.
You're suggesting that people visualize the atom using the outdated Bohr model. That's a bad idea. People should think in terms of quantum mechanics (QM). In QM one obtains a wave function whose physical meaning is that the modulus of that function, when its normalized, is the probability density. As such in one of the energy states there is a finite probability of finding the electron inside the nucleus.
 

Offline PmbPhy

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Re: Why aren't electrons in the nucleus?
« Reply #34 on: 22/06/2015 05:23:31 »
Quote from: jccc
what's difference between circle and orbit?
I doubt that you'll understand this or remember it for more than a few seconds but I thought I'd show it to you so that you'd have no excuses for saying that I never explained this to you, even though I'd explained it countless times.

This article describes the difference between Bohr orbits and atomic orbitals. See the first two figures in the following article:
http://mightylib.mit.edu/Course%20Materials/22.01/Fall%202001/why%20nuclei%20decay.pdf
 

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Re: Why aren't electrons in the nucleus?
« Reply #34 on: 22/06/2015 05:23:31 »

 

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