Re: The electron shell model - is far from being 'The story'
From: Bjoern Feuerbacher (feuerbac_at_thphys.uni-heidelberg.de)
Date: 11/04/04
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Date: Thu, 04 Nov 2004 19:00:31 +0100
FrankH wrote:
> maporat@012.net.il (Y.Porat) wrote in message > Hi Frank thank you for your very interesting information
>
>>yet while you mentioned the MIT people
>>1 lpease get to their attanetion the starnge fact that
>>the shelll model is not confirmed experimentally
>>for heavy elements
Please note that this is wrong. Porat simply does not understand
science. He thinks that as long as we don't have every tiny little
detail experimentally checked, we are not allowed to say that a theory
is experimentally confirmed!
>>*and yet no one was blinking an eye about it !!
>>
>
> Exactly what do you mean by "heavy" elements?
He talks about elements above iron. Some years ago, he asked in this
newsgroup up to which element QM works, and someone (I think Franz
Heymann) answered him that up to iron, the electronic structure of the
elements was analyzed in detail. What Porat does not understand here
(or, better, refuses to accept and understand) is:
1) Even for these cases, the analysis was done *theoretically* - by
computer calculation. The results were *not* all, down to the tiniest
little detail, checked experimentally.
2) It is no big problem today to use heavier elements than iron in
calculations, and this is done quite often. There is a vast literature
dealing with the chemical properties of molecules containing heavy
elements. The most prominent examples are that one can explain the
colour of gold and the liquidity of quicksilver, but there are hundreds,
probably even thousands of other applications. Hey, my own brother did
some work with platin halogenides!
3) This does not show in any way that QM does not work for elements
heavier than iron, and it also does not mean that QM was not checked
experimentally for these cases.
> I would say that the
> electron energy levels are experimentally well confirmed for at least
> up to krypton and this includes atoms which are fairly heavy (stuff
> like iron, copper, etc.). Do you have evidence that it hasn't been
> experimentally verified beyond a certain size atom?
He does not bother to provide evidence. He simply repeats ad nauseaum
what he was told years ago in this newsgroup (see above).
> Initially, I didn't believe the results that QM were producing because
> they were just a mass of abstract equations,
The same is true already for the application of Newton's theory of
gravity to the trajectories of celestial bodies, if you did not notice.
> I didn't know you could
> extract the electron energy levels by looking directly at the
> ionization energy.
Well, as I told you, this is not strictly true (only approximately).
Relaxation etc.
Oh, BTW, Porat seems to think that the "shells" are spatial structures.
He does not understand that the "shell model" is essentially only about
energy levels. Although I told him that several times.
> It produces the interesting pattern that the s
> orbits have 1 energy level, p 3 energy levels, d 5 levels. It matches
> the result predicted by QM without resorting to any math or equations
> or theory - it is a direct measurement. So I think you should take
> this experimental data and see how it fits into your model.
He does not bother explaining spectra. Although I asked him countless times.
> It is
> forcing me to rethink my model and so far, I do not have a solution.
Well, since the spectra were the original cause which led to
the construction of the atom model we have today, I would say that being
not able to explain spectra is quite bad when one attempts to construct
a new model...
> However, this doesn't mean that I believe in the Rutherford atom - at
> least not yet.
Good. You shouldn't - Rutherford's model (of electrons moving around the
nucleus like planets around the sun) was wrong, after all.
> I would agree that large angle backscattering can occur
> for reasons other than a massively charged nucleus and I did do some
> math and modelling to show that an octahedral shaped atom would result
> in similar scattering angles.
That's qualitative handwaving. Explain the observed dependence
of the scattering cross section on 1/sin^4(theta/2). Again: Rutherford
needed only a few months to explain that.
> I also don't think that the standard model of the atom really counts
> as a physical model
Define "physical model". I.e., define "physical".
> since it is difficult to see how the outer
> electrons shells actually interact to form chemical compounds
The shells don't "interact". When there are two (or more) nuclei, a
configuration where the electrons are mainly between the two nuclei (and
hence cause attraction and binding) simply has in general a lower energy
level than a configuration where the electrons remain located close to
the single nuclei.
> and as
> far as I know, QM isn't much help in predicting what chemical
> combinations are possible beyond some rules of thumb based on the
> valence electrons.
Wrong. It is indeed possible to do QM calculations on this. Simply use a
computer to numerically solve the Schroedinger equation. This is
absolutely standard stuff, done thousands of times every year.
You might try looking at this program description:
<http://wserv1.dl.ac.uk/CCP/CCP1/docs/>
This is one of several (I estimate 5 to 10) program packages used in
quantum chemistry in order to calculate the property of molecules:
binding strengths, binding angles, binding lengths, dipole moments,
excitation energies etc. etc. etc. And the agreement with the
experimental observations is usually quite good.
> So the standard model is more of a mathematical
> description of single atoms, but not a physical descriptions that
> helps show the physical constraints that govern chemical combination
> (something like how a lock fits into a key).
Define "physical description".
And please tell me why you expect that there *should* be general rules
here - after all, we are talking about systems with many (10, 20, 100,
1000, ...) electrons here in general! Since when are there any general
rules for systems consisting of a large number of particles? (please
notice that I don't mean a number which is so large that one can already
use statistical arguments, i.e. statistical mechanics and
thermodynamics). This does not even work in classical mechanics!
But what we *can* do is write down the Schroedinger equation for such
systems, put it onto a computer, and let the computer solve the equation
numerically. With good results. See above.
Bye,
Bjoern
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