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On 11/14/2013 04:47 PM, Bill Nettles wrote:
So the shell model of atoms with electrons implies the existence of
well-defined electrons? No, just the existence of a cloud of
electrons which have distinct groupings based on binding energy and
angular momentum. The cloud has Z (or Z-1, etc) -e charges and we
can recreate an individual electron if we put in enough energy. But
you can't get that electron as a separate entity until you give the
mass-energy back,
That /partly/ true but wildly exaggerated. We agree that
the electrons in an atom are in some ways different from
classical particles ... but so is every other electron,
whether in an atom or not.
There are /some/ experiments that you can /choose/ to do
that respond to all the electrons collectively, and that's
fine as far as it goes ... but please respect the fact
that other folks may choose differently.
In a sodium atom, all the electrons are identical particles,
but that does not mean they are indistinguishable. In the
ground state, there is *one* valence electron. It is
identifiable by its conventional spectroscopic quantum
numbers. I can flip its spin using ESR techniques. To
say that this electron is not really an electron is
unhelpful, to say the least.
There are things like charge and lepton number, each of
which is conserved and quantized, which help me count how
many electrons there are in the atom.
I can do high-energy Compton scattering to interact with
an individual electron within the atom, and for the
duration of the interaction the electron is essentially
a free particle.
A conduction electron in a wire is still an electron.
If you really think this is not an electron, you need
to come up with another name for it. Meanwhile everybody
else in the world will continue calling it an electron.
Sure, it's dressed mass is different from the free-
electron mass ... but the "free" electron is quite
heavily dressed, too.
A free electron in a CRT is still an electron, even
if it is a low-potential region. An electron in the
low-potential region near -- or in -- an atom is in
some ways different, but in very many ways the same.
You can pick pretty much any two things in the world
and say they are in some ways similar and in some ways
different. If you want to emphasize the differences,
I say OK, whatever, that's one way of looking at it.
When you say that's the only way of looking at things,
that's not good.
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