Question : His theory about the atom being a positive sphere and electrons being evenly distributed.
Answer : As you know, Thomson developed the rasin pudding model (or chocolate chip cookie if you prefer). He was correct that the atom was electrically neutral. He was mistaken in the distribution of the positive and negative particles in the atom. Thanks to Rutherford, we know that the atom contains a small positively charged nucleus. The electrons are outside the nucleus, not evenly distributed within a positively charged entity as Thomson suggested.
Question : Who discovered or created theories of the atomic structure besides these people: Democritus, John Dalton, JJ Thompson, Ernest Rutherford, James Chadwick, and Neils Bohr?
Answer : Albert Einstein. Richard Feynman. Max Planck. Madame Curie. Niels Henrik David.
Question : I searched on google and everything, but it didn't say how he contributed to the atomic theory. I know about the gold foil experiment, but I don't really understand it. Please help. I did the search, I just couldn't find the right answers.
Answer : The main change that was brought about by Rutherford's gold-foil experiment was the change in conception of the structure of the atom. After Rutherford's experiment he began developing an orbital theory for the placement of electrons in an atom. Although this model was not entirely accurate, it allowed Niels Bohr to create his model of the atom, which was has been the standard since 1911 (although currently scientists describe it slightly differently, the application of the Bohr model has remained unchanged in almost all respects, with the exception of quantum physics).