Re: Protons & electrons attractions

Sam Wormley wrote:
> Watclod wrote:
> > Can anyone give the best descriptions or layman explanations
> > why electrons don't fall into the protons.
> >
>
> Probably the best reference for more information on this (though it
is
> pretty tough sledding) is PW Atkins' "Molecular Quantum Mechanics."
>
>
http://van.hep.uiuc.edu/van/qa/section/New_and_Exciting_Physics/Inside_the_Atom/968623363.htm
>
http://www.google.com/search?q=why+electrons+don%27t+fall+into+the+nucleus

Interesting site especially the first. The explanations why electrons
don't fall into the nucleus is a bit out of the ordinary. No wonder
there are 101 other interpretations being offered by crackpots.
Anyway. How come when the electron cloud squashes closer to the
nucleus, the kinetic energy goes up as described by the following:

The picture you often see of electrons as small objects
circling a nucleus in well defined "orbits" is actually quite wrong.
As we now understand it, the electrons aren't really at any one place
at any time at all. Instead they exist as a sort of cloud. The cloud
can compress to a very small space briefly if you probe it in the
right way, but before that it really acts like a spread-out cloud.
For example, the electron in a hydrogen atom likes to occupy a
spherical volume surrounding the proton. If you think of the proton
as the size of a grain of salt, then the electron cloud would have
about a ten foot radius. If you probe, you'll probably find the
electron somewhere in that region.

The weird thing about that cloud is that its spread in
space is related to the spread of possible momenta (or velocities) of
the electron. So here's the key point, which we won't pretend to
explain here. The more squashed in the cloud gets, the more spread
out the range of momenta has to get. That's called Heisenberg's
uncertainty principle. It could quit moving if it spread out more,
but that would mean not being as near the nucleus, and having higher
potential energy. Big momenta mean big kinetic energies. So the
cloud can lower its potential energy by squishing in closer to the
nucleus, but when it squishes in too far its kinetic energy goes up
more than its potential energy goes down. So it settles at a happy
medium, with the lowest possible energy, and that gives the cloud and
thus the atom its size.

.

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