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Re: Peroidic Table (was exclusion principle which was electrons)



Josh Green wrote:
shells are something we can "see" from atomic diameters. This would
eliminate the possibility of all the electrons filling in the first shell,
since we know that the third electron fills in another shell. This comes
not by theory, but by observation, which is explained by shells of
different
levels.

Why can't the observation of atomic diameters be explained by electrons
spherically milling about the nucleus building outwards with increasing
population (up to 92 for the naturally occuring elements)? If, by
observation, you really mean evidence for shells, like the changes noted in
successive ionization energies of an element, fine. But diameters? Also, I
disagree that we can 'see' shells or orbitals as these are mathematical QM
constructs.

If electrons don't simply mill around the nucleus, but do form up in shells,
then what set of shell rules do they obey? We have devised a set of
mathematical rules that seems to fit the observations of chemical
properties, with a basis in numerology, if that's what you want to call
quantum numbers, and a knowledge of the number of electrons in an atom. The
exclusion principle is one of the fundamental mathematical rules.

Applying these rules requires a bit of jiggery- pokery too, like starting to
fill outer shells before inner ones are full, without any numerological
(mathematical) basis for doing so, only knowing that it is a necessary
proposal if the mathematical rules are to fit the observed properties of
elements. Nobody has determined, ab initio at least, why this should occur,
be it from a consideration of atomic number only, or using any of the
quantum numbers associated with atomic theory.

Nuclear charge (hence Z) only partly determines the potential energy of an
electron in a multi-electron atom (albeit that it determines the number of
electrons in the case of a neutral atom, and thus is of arithmetical
consequence only). Perhaps if we had a full mathematical understanding of
such atoms instead of the approximation based on the H-atom we are currently
stuck with, and if the exclusion principle was then found to be a direct
consequence of atomic number, then Josh would have an argument. Somehow, I
think the basic premise that no two electrons can occupy exact same energy
states would be a part of any new theory, and would simply have to be
accepted as it is now, with no real understanding of why it has to be.

Perhaps the last sentence touches more on the original question posed by
Josh about electrons.