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Democritus
Democritus was the first person to think that if you kept cutting something in half over and over again then you would eventually end up with one particle, which he called an atom, that can't be cut anymore. He thought that the atoms were small hard particles that were made of one material which formed into different shapes and sizes. His model was the atom and he thought it looked like a solid spherical shape. -
Dalton
Dalton thought that elements combine in certain proportions to make compounds. He published his atomic theory which said, all substances are made from atoms, atoms are small particles that cant be created, divided, or destroyed, atoms of the same element are exactly the same and atoms of different elements are different, and atoms join together to make new elements.His atom model was called the billiard ball model and he thought it looked like Democritus’ model looked like. -
Stoney
Stoney came up with the term electron, which he said was the “fundamental unit quantity of electricity”, and he estimated the charge in a hydrogen atom. -
Thomson
Thomson found a mistake in Dalton’s theory and said that there are even smaller particles inside the atom. This means that atoms can be divided even smaller and that there were negatively charged particles in the atom which were mixed throughout the atom.Thomson’s model was called the plum-pudding model and he used his experiment, the Cathode-ray tube, to find out that there were negatively charged particles in every type of atom. -
Rutherford
Rutherford studied the parts of an atom and thought atoms should be considered mostly empty space with a tiny bit of highly dense matter. He thought the center of an atom was small, very dense, and positively charged and he called it the nucleus. He also thought that there were positively charged particles that went around the nucleus but were pushed away by the positively charged nucleus. Rutherford found his model by using his Gold Foil experiment. -
Millikan
Millikan measured the amount of energy in an electron and he worked on the photoelectric effect -
Bohr
Bohr thought that electrons moved around the nucleus in certain paths/energy levels. He didn’t think that there were any paths between the different levels but that the electrons were able to jump from path to path.His atom model was called the Bohr-Rutherford model because he worked with Rutherford. -
Schrodinger
Schrodinger thought that electrons were continuous clouds and he wrote that wave mechanics were a mathematical atom. -
Chadwick
Chadwick proved that neutrons existed and that they help stabilize the protons in the atoms nucleus. Protons do not have an electrical charge and they are packed tightly together with protons in the nucleus. -
Fermi
Fermi conducted the first chain reaction releasing energy from the atom's nucleus.
