Everyone at that time imagined the atom as a "plum pudding." That is ... He realized that Rutherford's model wasn't quite right. By all rules of classical physics, it should be very unstable.

Most of an atom is empty space ... To explain how atoms were overall neutral, he proposed the “plum pudding model” in 1904. As the alpha particles were known to have a lot of energy and ...

Changes to the atomic model Atoms can be broken down into smaller parts. An atom is made of tiny negatively charged electrons dotted about a positively charged sphere like a plum pudding.