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442 BCE
Pre-Scientific DEMOCRITUS
Democritus a philosopher thought that to find the smallest pieces that made up everything were called atomos, saying that if everything was cut into smaller and smaller pieces he would have to stop somewhere, this somewhere is his idea of the Atomos -
380 BCE
Pre-Scientific Heraclitus
Heraclitus was a philosopher who thought that everything was made out of fire, that all things were created by fire and all things would return to fire.
Information was found from the website below. http://www.iep.utm.edu/heraclit/ -
340 BCE
Pre-Scientific Aristotle
Aristotle was another philosopher who thought that everything was made from the four elements, so everything could be narrowed down to fire, water, earth and air. -
Dalton's Atomic Theory
Dalton created his five postulates
-All matter is made of extremely small particles called atoms.
-Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
- Atoms cannot be subdivided, created, or destroyed.
-Atoms of different elements combine in simple whole number ratios to form chemical compounds.
-In Chemical reactions, atoms are combined, separated, or rearranged -
J.J. Thomson's Atomic Theory
J.J. Thomson with these things called cathode ray tubes which were designed to show particles moving through tubes, and when he placed magnets on the sides of the tube he realized the light particles bent to the positive particles and moved away from the negative particles, telling him that all atoms was made from these particles which he named electrons. Since he found that these particles have a negative reaction there has to be a positive element to it as well to balance it out. -
The Plum Pudding Model
J.J. Thomson also created the Plum Pudding Model saying that since he knew that all atoms had a neutral charge and that these atoms he found also had a negative charge meant that atoms had to have a positive charge that cancelled out the negative charge. He explained this as a plum pudding because a plum pudding also is mixed of multiple different things. -
Rutherford's Experiment
Rutherford discovered that the atom was not just a soup of negative and positive charges but that it had a dense core made of positive particles, and electrons floating around the positive particles. He found this through experimenting with positive alpha particles and shooting them at a gold tin foil. since a lot of these particles missed their target he knew that the positive part of the atom was not all over but focused on one central point in the atom. -
Bohr's Atomic Theory
Bohr was testing atoms and found that Rutherford's experiment was only partially correct. Bohr was testing what would happen if you shot energy into the atoms, when he did this he realized that for different atoms there were different lights coming from these atoms. Because of this he knew that atoms were not found randomly in an atom but on specific segments of the atom. -
Schrodinger's Atomic Theory
Schrodinger found through many tests that an atom could not orbit the protons like it does in Bohr's model. He found that electrons were actually found in an electron cloud. These atoms showed different lights because the atoms do have different charges, but were they are in the atom doesn't really matter. -
Chadwick's Electron cloud model 2.0
Chadwick had the same idea as Schrodinger, but he questioned why the atoms were as heavy as they were and wondered were the extra mass came from. He experimented this by shooting alpha particles at atoms and found that inside the nucleus it wasn't only protons but there was a neutral particles as well, these particles were the things that added to the mass.
