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Democritus
A Greek philosopher named Democritus philosophied that you would eventually end up with a particle that you couldn't cut. He called the particle an atom coming from the Greek term atomos-- meaning "not able to be divided." The Greek philosopher thought that atoms are small, hard particles that were made of a single material and formed into differnet shapes and sizes. -
John Daltoon
Dalton wanted to know why elements combine in certain proportions based on mass to form compounds. His theory stated that all substances are made of atoms-- they cannot be created, divided, or destroyed. He also said that atoms of the same element are exactly alike, and atoms of different elements are different. The last part of his theory read that atoms join with other atoms to make new substances. His theory however, was not quite right and has changed over the years to fit new informaton. -
J.J. Thomson
Thomson discovered that Dalton's theory was wrong. He found that there are small particles inside the atom.That means that atoms can be divided even smaller-- makeing Dalton's theory wrong. When Thomson found this information he built a model that was often called the plum-pudding model. -
Ernest Rutherford
Rutherford designed an experiment were he aimed a beam of light a thin gold sheet of foil and put a special coating behind it-- to study the parts of the atom. He could then see where the particles went after hitting the gold. -
Ernest Rutherford
In this year, he revised his atomic theory. He made a new model of the atom and proposed that in the middle of every atom there was a tiny, dense particle called a necleus. It is also positivley charged, he said. -
Niels Bohr
The Danish scientist, who worked with Rutherford, proposed that electrons move around in certain paths, or energy levels. Bohr also made a model that was helpful, but there was no room for improvment. -
Erwin Shrodinger and Werner Heisenberg
Both 20th-century scientists helped us understand our current atom. They went into depth about the atom, explaining that electrons do not travel in certain paths-- proving Bohr wrong. -
Aristotle
Another Greecian, Aristotle, disagreed with Democritus's theories. He said you could never end up with a particle that was so small you couldn't cut. Most people thought he was right for a long time because he had a big influence. Democritus was right though.
