posted by sam .
I have read over 20 sites and I still cant figure this one out - in an atom electrons are located in energy levels that are a certain distance from the nucleus.
The statement is not really true. It represents the old-fashioned and simplistic Bohr model of the atom.
In the correct quantum mechanics theory of the atom, the electrons occupy a region around the nucleus like a cloud, but you cannot track exactly where they are. You can only predict the probability that one will be found in a certain place. Most electrons are within about 10^-10 m of the nucleus. There are different orbit probability density "wave functions" for differect electrons. Some are much closer than others.