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460 BCE
Democritus
Democritus developed the idea of atoms. He asked if you keep breaking something in half, how many breaks will you get until you can no longer break it in half again? He thought that it had to end at some point, ending at the smallest piece of matter. He called this an atom. -
Period: to
Dalton
Dalton created the Solid Sphere Model. He was the first scientist after Democritus to start experimenting on atoms again. -
Thomson
J.J. Thomsom discovered the electron and came up with a model for the structure for an atom. It was called the Plum Pudding Model because it looked like raisins in pudding. -
Planck
Max Planck discovered that if you vibrate an atom strong enough then you can measure energy in small units. He called this energy packets, quanta. -
Einstein
Albert Einstein wrote a breakthrough-paper about how light absorption can release electrons from atoms. This was called the "photoelectric effect." He recieved his only Nobel Prize in physics in 1921 for this discovery. -
Rutherford
Earnest Rutherford proved that if you bombard atoms with alpha rays, you could see what the inside of an atom looks like. He used Radium as a source for the alpha particles and shined them onto the atoms in the gold foil, and behind the foil was a fluorescent screen where he could observe the alpha particles impact. -
Bohr
Niels Bohr created the The Bohr (Planetary) Model. He also came up with a theory that said the electrons do not spiral into the nucleus and came up with two rules for what does happen. -
Pauli
Wolfgang Pauli predicted that an atom should spin like a top while it orbits around the nucleus. It can spin in either direction. -
Broglie
Louis de Broglie wondered why atom particles couldn't also behave like waves. He used a few equations derived from Einstein's E=mc2 to show was matter waves would behave like if they existed at all. Experiments later proved his theory correct. -
Heisenberg
Werner Heisenberg had his own theory called matrix mechanics which also explained the behavior of atoms. Heisenberg and Schrödinger's theories had entirely different assumptions but they both worked; mathematically, they appeared the same. -
Schrödinger
Erwin Schrödinger used the particle waves to go all the way to form a model of the atom. His theory worked ;ole the harmonics on a violin string except the vibrations traveled in circles. He gave his theory of wave mechanics the "psi" symbol. -
Chadwick
James Chadwick discovered the neutron. He discovered it was slightly heavier than the proton with a mass on 1840 electrons and with no charge. -
Timeline
I'm making this timeline about the history of atoms, and gracious I hope I did it right. :)