Okay so basically Dalton (1803) hadn't had much knowledge of the atom since it was so early in the atomic theory timeline and the technology wasn't as developed. He pretty much thought the atom was a small spherically shaped particle. J.J Thomson discovered the electron but had not known what the nucleus was yet (1897-98). Ernest Rutherford now knew that atoms were not the smallest parts of matter, he believed something was surrounding the nucleus. Niels Bohr had been known to have created the Bohr model, he also discovered that electrons surround the nucleus. Today we know that atoms are made up of even smaller particles called protons, neutrons, and electrons.
Hope this helps, make sure to put it in your own words. Let me know if you need any more help :)
