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492 BCE
Democratus
Democratus cut stone into smaller and smaller peices until they could no longer be divided. He was the first person to actually give proof of atoms existents. He believed that atoms were hooked together and could only be broke apart at the seams. He also believed that atoms couldn't be broken anymore. -
John Dalton
John Dalton mixed gases to determine what the individual gas contributed to the mixture as a whole. He discovered the first atomic theory of matter and that sizes of particles that make up gases must be different. -
J.J Thomson
J.J Thomson used cathode rays to determine his theory that some things had a negative charge. Cathode rays had a negative electric charge that were much smaller than an atom. He also believed that all atoms had these. They are now known as electrons. -
Ernest Rutherford
Ernest Rutherford used alpha particles and shot them at a thin metal foil. Some of the particles went straight threw the metal but some bounced back. He traced them to determine to size of the nucleus. He developed the nuclear model of the atom and discovered that J.J Thomson's theory was flawed. -
Niels Bohr
Niels Bohr discovered that Ernest Rutherford's model wasn't completely correct. He determined that the electrons must orbit around the nucleus, because if they didn't it would be very unstable. The model of the atom was renamed to the Bohr-Rutherford model.
