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400
Democritus
Democritus believed that all matter consisted of small particles that couldn't be divided. He talked about his theory making others believe his theory was right. -
401
Aristotle
Aristotle beleived all substances were built from four elements: fire,water,earth, and air. Created a diagram showing the elements and hot,cold,dry, and wet. -
John Dalton
His theory said all elements are composed of atoms. Also all atoms of the same element have the same mass, and atoms of different elements have different masses. Created spheres to illustrate what atoms looked like. -
Joseph Thomson
Thomson used electric current to study atoms. He hypothesized that a beam has a stream of particles that interact with the air in the tube he created. Some refer to his model as the "plum pudding." Model showed that the negaitve and positive charges are balanced. -
Niels Bohr
His theory was that electrons move with constant speed in fixed orbits around the nucleus. He drew a atom with electrons orbiting it. -
Hantoro Nagaoka
He suggests that an atom has a central nucleus. Electrons orbit this center nucleus. Drew a diagram of his theory. -
Robert Millikan
Determined the unit charge of an electron in 1909 with his oil drop experiment. e = 1.60 x 10-19. -
Ernest Rutherford
He discovered that uranium emits fast moving particles that have a positive charge. With help from Marsden he shot a beam of light at a gold piece to see where light travels first. -
Albert Einstein
Came up with the equation E=mc2. E represents energy, m represents mass, and c² is the square of the speed of light. -
Erwin Schrodinger
Used mathmatical equations to describe the movement of electrons. His model was made into an electron cloud. -
Ernest Marsden
Helped with Rutherfords theory and model. He was one of Rutherfords students. He helped with the gold piece and beam of light model. -
James Chadwick
He confirmed there are neutrons. Neutrons stabalized the repeal of the positive protons. -
Louis de Brogile
Said moving particles such as electrons have some properties of waves. He tested his theory by shooting electrons at nickle.
