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460 BCE
Democritus
Democritus was a pre-Socratic Greek philosopher who developed the atomic theory. In essence, his theory was that everything is made up of the most basic thing- atoms. He believed that if you broke something down, you would eventually reach a point where you could break it down no further. This was an atom. For example, if you broke a rock in half over an dover, you would eventually reach a point where you could break it no more, and this was an atom. -
John Dalton
John Dalton was an English chemist who created the first chart of atomic weights. This contribution helped scientists determine weight universally. -
J.J. Thomson
J.J. Thomson was an English physicist who discovered the electron. He did the gold foil experiment with fellow physicist Ernest Rutherford, who discovered the proton. The gold foil experiment consisted of Thomson and Rutherford shooting alpha particles at gold foil and recording their findings. Sometimes, the alpha particle would go straight through with no problem. Other times, they would go in random directions. This led them to the conclusion that there was a lot of empty space in atoms. -
Ernest Rutherford
Ernest Rutherford was a physicist from New Zealand who discovered the proton. He did the gold foil experiment with fellow scientist J.J. Thomson. They were firing alpha particles at a piece of gold foil for an experiment to see how they reacted with the gold. More on that with J.J. Thomson. -
Niels Bohr
Niels Bohr was a Danish physicist who explained what goes on inside an atom. His theory stated that electrons move in certain orbits around the nucleus, rather than it being random movement. -
Erwin Schrodinger
Erwin Schrodinger was an Austrian physicist who developed the Schrodinger wave equation. His theory is what we use today: the electron cloud model. In essence, rather than electrons going around the nucleus in a defined orbit, they move around it. While there is some rhyme and reason to how they move, it is not as defined as Bohr's model suggests. -
James Chadwick
James Chadwick was an English physicist who discovered the neutron in 1932. he was awarded the Nobel Prize in Physics for this discovery. This contribution helped to make the atomic bomb possible.
