I had some questions about this too. I also asked it on a different folder, but here it is: I'm hoping someone has a good analogy or way to explain this, which I understand in terms learning the words, but I don't have an intuitive understanding of it. Why don't electrons fly into the nucleus? Electrons are negative, the nucleus is positive, in we go! Much like planets around the sun, I'm sure some electrons would end up in orbit. The electrons have 'too much energy' (going too fast?), and the harder the Nucleus tries to pull them in, the tighter they would spin around the nucleus, never going in. 3 problems I don't grasp about this: 1) If you have a row of copper atoms, for instance, and you pass a current through it, no electrons end up inside any of the nuclei? How come? If I shoot an asteroid straight at the sun, it's going in, not orbit! There's the concept of electron clouds and shells and probability and such, but an electron is a discrete thing. We can shoot a single electron in a vacuum tube at a target and hit it exactly (like we used to do with TVs). On old vacuum tubes we could carve shapes on the inside of the tube with an electron stream. If I line up an electron exactly to a bare nucleus (a nucleus with no electrons orbiting it), would the electron not fall right in? 2) if I have a metal table, and I press down on it with my hand, the table electrons are not pressed into their nuclei? why? If I put a rocket on the dark side of Venus that pushes Venus towards the sun, it's eventually going in! (Venus works 'cause the same side faces the Sun constantly - a rocket on the dark side would push perpendicular to the tangent of Venus' orbit - straight towards the Sun!) 3) Sometimes Electron-like radiation, escape from inside the nucleus. That just doesn't make sense. A tiny negative charge flying away from a giant positive charge? Specially since it happens in nuclei that are big with a huge positive energy, like Uranium. It seems like only the power of a neutron star is strong enough to force those electrons in, and I just can't understand that. Electrons are tiny, it seems like much smaller forces could do the job.