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400 BCE
Democritus
Democritus had no technology available at the time and did not complete any experiments.he had no proof that the atom existed and no evidence to back up his claims.Democritus did not pretend to know what atoms actually looked like,however,he believed that theses really small particles were completely solid and would come out endless -
John dalton
Dalton used data from experiments that he and other scientists conducted by mixing various gases together he also used the recent knowledge of that water is made of two elements (oxygen and hydrogen)Dalton's overall idea of atoms did not come far from Democritus's original idea.He did believe however that atoms were small solid spheres.These spheres would be slightly different depending on the type of element the matter was made of. -
J.J Thomson
Much of Thomson's work dealt in experiments with charged particles.In order to discover more about the nature and structure of atoms, Thomson shot rays of charged particles through a glass tube called a cathode ray tube.He placed a positively charged plate on one side of the tube and a negatively charged plate on the other side.When the rays of charged particles shot through the tube, he noticed that the rays would always move away from the negative side and were attracted to the positive plate. -
Ernest Rutherford
Even though electrons had been recently discovered, not much was really known about the actual structure of the atom.Rutherford put Thomson's Plum Pudding Model to the test and showed that it was wrong.Rutherford discovered that most of an atom is actually completely empty space.Instead being solid all the way through, Rutherford discovered that most of the mass of an atom is actually located in a small central nucleus that is positively charged. -
Niels Bohr
After Rutherford's discovery of the nucleus, scientists were perplexed as to where an atom's electrons were actually located. Bohr set out to learn more about the movement and placement of electrons. He discovered that electrons have specific amounts of energy and move in orbits. Bohr also noted that the orbit that an electron moves in is determined by how much energy the electron has.
