So what's wrong with the neat circular atom? Plenty. To start with, there are lots of paths an electron can take in order to get around the nucleus. Turns out, there's no reason to assume that electron orbits are circular. In fact it's very rare for an atom's electron to be in a circular orbit.

Here's a more accurate picture of what that electron might be doing:

Here are some things that make this model better than the one with the circle:

• The electron's orbit is no longer a circle. Now it looks like a "stretched circle," or an ellipse.
• The electron moves at different speeds. Fast near the nucleus and slow when it's far from the nucleus.
• The electron is not always the same distance from the nucleus. Sometimes it's close, other times, it's far away.

BUT...