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Democritus
Democritus was a Greek philosopher. Democritus began to think; what happens if you keep cutting an object in half? He reasoned that it would eventually be uncuttable. He called these particles Atomos or indivisble. He decided that they were made up of one matieral and could form into every other object. -
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Aristotle
Aristotle, a respected philosopher, disagreed and thought these particles could be cut over and over again. everyone believed in Aristotle for many years until John Dalton. -
John Dalton
John Dalton was a British school teacher and chemist. He was perplexed on the matter of why elements combined at certain ratios or proportions.His expirements led him to believe that each elemnt were made up of single atoms. When he published his theory, he stated that:
All matter is made up of atoms, and atoms can't be destroyed.
Atoms combine to make new compounds.
Atoms in one element are alike. -
J.J. Thompson
J.J. Thompson was a British scientist like Dalton. He discovered a flaw in Dalton's theory. He discovered that thers are smaller particles in the atom. Using a Cathode-Ray tube, he discovered that magnetic fields affected the stream of electicity. He discovered an even smaller particle: the electron. He called his theory the plum pudding model because he thought the electrons were mixed through the atom like raisens in a plum pudding. -
Ernest Rutherford
One of Thompson's students, Ernest Rutherford, decided to test Thompson's theory. His expirement involved a piece of radium surrounded by lead shooting postive charged particles at a piece of gold foil. The gold foil was surrounded by a special matieral that would show the place of of where the particles hit. However he was excited and perplexed when some particles appeared to have been deflected; even sent straight back. The rest went straight like he thought they would. -
Ernest Rutherford
He reasoned that in order for particles to pass through, the aroms must have alot of space. However, for the particles to bounce back, there had to be some sort of high concentration of particles. He called this part the nucleous, and because like charges repel, the electrons went around the nucleous. -
Niels Bohr
Niels was a Danish scientist who worked alongside with Rutherford. He studied how atoms react to light. He thought that electrons were organized by energy levels around the nucleous in direct paths but can't be in the middle of two paths. -
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Erwin Schoedinger and Werner Heisenberg
Following the information provided by Bohr, an Austrian and a German physicist improved the atomic theory. They discovered that electrons are organized into energy levels, but they can't be found on one specific route. Instead, they could be anywher in what they called Electron Clouds.