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© Copyright 1999, Jim Loy
I'm sure you have seen pictures of atoms, looking like the one at
the left. This represents a lithium atom (with 3 electrons). We are sometimes
told that this is how Niels Bohr described the structure of the atom. And some
people have even wondered if this miniature solar system has tiny people living
on the electrons.
While this can be a useful diagram, it was known from the beginning that electrons do not orbit the nucleus. An orbiting electron would be constantly accelerating (changing direction, in this case). An accelerating charged particle would emit electromagnetic radiation (light or something similar). This would mean that the electron would be losing energy. And, it would spiral into the nucleus, in a dramatically short time (a microsecond or so). An atom, with orbiting electrons, is not stable.
So, what is the situation? The electrons are like a cloud around the nucleus. They do not exist at any exact place outside the nucleus, but are spread out over a volume.
In the above diagram, the nucleus should be much much smaller, too small to show up in the diagram. Although it contains almost all of the mass of the atom, the nucleus occupies a very very tiny percentage of the volume of the atom.