He came up with the idea that everything is made up with very tiny balls.

He proposed that all matter are made out of atoms and that they were indestructible and individual. He also thought that 2+ atoms make a compound and they can be rearranged to make different compounds.

He proposed the combustion theory that was based on mass measurements.

JJ Thomson proposed the plum pudding model that is composed with electrons.

He did an experiment that contributed hugely in the understanding of atoms and the atomic theory.

Rutherford used Thomson's model and used his own experiment and demonstrated that atoms have very tiny but heavy nucleus.

Proposed a theory for the hydrogen atom on quantum theory.

He included quantum mechanics that was all based on the quantum theory so that he could interpret behaviors of particles and atoms.

Took Bohr's atom model a bit furhter by using math equations. This model is now known as the quantum mechanical model of an atom.

He did research and predicted the kind of waves electrons had naturally.