John Dalton was a chemist from England, born in 1776 and died 1844. At the time the theory of atoms weren’t well supported, Greek philosopher Democritos said that matter could be divided to the point where there’s only be one thing left, the atom. But there was a lack of cold hard evidence on whether on it was was true as the Greeks could not find a way to support Democritos’ theory. Years later Dalton came up with the idea that Atoms can be told apart on their atomic weight. Dalton also discovered that atoms can’t be destroyed nor created, as well as stating in his book, A New System of Chemical Philosophy, saying that atoms in a specific element will be the same in terms of size and weight, but if you were to take another element the atoms and compared the two elements, it would be completely different. Dalton discovered that compounds are combinations of different atoms and that chemical reactions are the reordering of atoms. Dalton mainly based his ideas on the Democritos, law of conservation of mass, and law of constant composition. What was incorrect of Dalton was that he stated Atoms were invisible as they can be broken down into protons, neutrons, and electrons. Adding on, he made the comment that atoms of the same elements are the same but they can all vary with their density and masses. Dalton was correct on that all matter consists atoms and they can’t be made or destroyed. Joseph John “JJ” Thomson was an English physicist, born in 1856 and 1940. Much from the advancements of the thoughts surrounding Atoms thanks to Dalton, at the time many assumed that Atoms were purely invisible and that was it, nothing made it up as it was just an atom and there was nothing to it. During that period of time it had been unknown there were things like neutrons, protons, and electrons, that was until Thomson stepped in with his Cathode ray tube. Basically Thomson discovered that in fact an atom can be broken down, discovering the first of the three subatomic particles, being the electron. Noticing that the Cathode rays particles contained negative charge and positively charged atoms in Neon, being this he saw the model of the atom that was used at the time lacked both positive and negative charges. Being this he went on to create the Plum Pudding which was his model of the atom where the raisins represented the negatively charged electrons, with the raisins being surrounded by pudding representing the not yet discovered protons or positives. It’s not specifically stated on where and what Thomson based his theories and discoveries on, but it can be assumed it was based off of Dalton and his evidence of the existence of the atom. Thomson got wrong the Plum Pudding model of an atom incorrect as it was disproven later on by Rutherford since he thought that the positive charge of an atom was a uniform ball with the electrons floating and moving. But he was correct on the negative charge an atom (electron), as it can be broken down. Ernest Rutherford was a New Zealand born British physicist, born in 1871 to 1937, and mostly worked in England. At the time JJ Thomson’s model of the atom, Plum Pudding, was mostly regarded as the standard of what the atom had looked like but then it had been proven wrong in 1905. The atom was basically a sphere of positive charges and chunks of electrons contained inside floating and moving around. This was until Ernest Rutherford came through in 1911 with his experiments known as the gold-foil experiment. Which shook the science community with his new and improved version of the model, coined the Rutherford model. Atoms contain protons and neutrons which was known at the time, but the million dollar question was how were these placed and what did an atom actually look like. The gold foil test was to help prove Thomson’s theory that the mass of an atom is evenly spread throughout. Rutherford shot high velocity alpha particles at gold foil and as expected they went though the atom but to his shock some had bounced back. With this experiment Rutherford concluded with a new model of the atom, deriving away from Thomson’s Plum Pudding. This new model had a nucleus in the middle which inside contained protons with the electrons outside of it orbiting around, like the Sun. Rutherford’s theory can most likely be based off of just pure physics and the work previously done by Thomson as his model seemed highly probable as a basis for the Rutherford model. Rutherford can be assumed to have been curious or inspired by the Plum Pudding model and began to test out experiments on the Plum Pudding model. What Rutherford got incorrect on his view of the atom was that his theory on the electrons orbiting around the nucleus packed electrons, as if it was by what Rutherford thought the electrons would spin and orbit but lose energy after a few spins, if that were to happen an entire atom would fall apart. But what he did correct was with the discovery of the Nucleus in the middle of the atom and proved the Plum Pudding model incorrect. Niels Bohr was a Danish Physicist born in 1885 and died 1962. At the time it was known that there were electrons that orbit around a nucleus (which isn’t the case), as Rutherford’s model at the time was the only widely regarded model of the atom. That the protons were packed into the nucleus with the electrons around outside just orbiting around it, like the planets and the Sun. But then Bohr did research and concluded that instead of what Rutherford had discovered, rather the atoms had different orbit levels for the electrons travel. That atoms send electromagnetic radiation because of the electrons traveling around from different orbit levels. His discovery ultimately tweaked the design and model of the atom. Bohr based his theory on Albert Einstein and his work of the Special Theory of Relativity, who based off his work off Max Planck’s discovery of quantized energy. What Bohr had been wrong on was that the atom isn’t a flat plane that goes in a circular motion, but modern science has proven that it’s more 3 Dimensional and not this flat plane where the electrons orbit around.