One is the plum pudding theory by Thomsons that theorized that positive and negative charges were randomly distributed in an atom. This was later discovered that the positive charge was located at the small nucleus center of the atoms and negative electrons on the outside.
Another is the aspect in Bohr model theory that electron orbit the nucleus like planets orbit the sun. Quantum mechanisms have come to disprove this and identify that electron orbit can only be predicted by probabilities and not in the certainty of their position around the nucleus of the atom. They randomly skip and hop (disappear and reappear) at positions around the nucleus.
