Re: Basic question about atoms

Matt Gregory wrote: 
I'm not a physics enthusiast, all I know is what I learned in high
school: that an atom has a positively charged nucleus which
negatively charged electrons are in orbit around.

Unfortunately, this is already wrong: the electrons are *not* "in orbit around". Don't picture them as little marbles flying around the nucleus like planets around the sun. A better picture (still not the truth, only a visualization!) is that the electrons form "charge clouds" around the nuclei.


I want to know what is the theory that explains what causes atoms
to stick together in a solid. 

Quantum mechanics.


If the perimeter of an atom has a
negative charge, then why don't the atoms fly apart (or fall apart
at least, if the charge of the nucleus balances the charge of the
electrons).

It's much easier to first look at a simple molecule instead of going to a solid at once. Let's look at the hydrogen molecule, H_2, i.e. a molecule consisting of two protons and two electrons. Now picture the "charge cloud" of the electrons to be concentrated between the two protons (see e.g. fig. 6-2 at
<http://www.chemistry.mcmaster.ca/esam/Chapter_6/intro.html>)
Both protons are attracted to this charge cloud, but they also repel each other. There is one distance between the protons where these two forces exactly cancel out each other. Then you have the stable configuration of the molecule.

Does this help?


Bye,
Bjoern
.

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