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100
Democritus
He asked whether matter could be divided infinitely or if it has a limit on how small matter could go. He called the smallest partcle "atomos", meaning "not to be cut". He thought there was an empty space, a void where atoms could move from place to place. His ideas disagreed with Aristotle's and were ignored for about 2000 years. -
100
Aristotle
He strongly disagreed with the atom, he had incorrect ideas about the laws of motion, including that he believed that since an infinite speed was impossible. This helped him state that a void wasn't possible. He thought the earth was made up of the four elements, not atoms. -
Pierre Gassendi
Agreed with Epicures theory of atomism. Said to be the founder of modern atomic theory. -
John Dalton
Introduced the idea of the atom on a solid scientific basis. His theory explained things we hadn't been able to figure out until that point and his theory is still used today, even though its two centuries old. -
JJ Thomson
He discovered the electron, and the atom was shown to have an internal structure. He also proposed a structure for the atom, and estimated the charge of the electron. -
Ernest Rutherford
Rutherford did some experimenting and found that atoms are not empty space, that they have a nucleus. He overturned Thompson's model (Plum Pudding). -
Niels Bohr
He proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. He said that electrons moved in prescribed orbits. He worked with JJ Thomspon and Ernest Rutherford. -
Francis Aston
He worked with JJ Thomson to study positive rays, then went on to discover isotopes (using neon). He invented the mass spectrograph, which helped him discover isotopes. -
Gerd Binnig & Heinrich Rohrer
They invented the Scanning Tunneling Microscope (STM), allowing the first images of individual atoms on the surfaces of materials to be made.
