he said matter is composed of small indivisible particles called atoms
all elements are composed of indivisible atoms
atoms of the same element are exactly alike, and atoms of one element are from atoms of another element
compounds are formed when two or more atoms are chemically joined
in a chemically reaction atom are rearranged but not changed
He believed that the atom was composed of a positively nucleus that is surrounded by negatively charged electrons to balance the charge. He used a Cathode Ray Tube to test this. He made a "Plum pudding model" to model this.
Rutherford made the gold foil experiment to prove that there was a nucleus in the center of an atom. He concluded that there is a nucleus and there is mostly empty space.
Bohr explained why electrons don't fall into the nucleus by creating a planetary model that shows the electrons orbiting the nucleus of the atom.
Schrodinger made the quantum mechanical to predict the location of an electron. The nucleus is surrounded by an electric cloud. Where the cloud is most dense, the electron is less likely to be in a less dense part of the cloud