-
200
440 B.C- Democritus
He thought that you would eventually end up with a particle that cannot be cut. He called this particle an atom. -
400
B.C 440- Aristotle
He believed that you would never end up with a particle that could not be cut. He disagreed with Democritus's idea. -
John Dalton
John Dalton experienced with different substances, his results suggested that elements combine in certain porportions because thay are made of single atoms. He published his atomic theory in 1803. -
J.J Thomson
Showed that there was a mistake in Dalton's theory. He discovered that there are small particles inside the atom. Atoms can be divided. -
Period: to
The Development of the Atomic Theory
-
Ernest Rutherford
He started an experiment with Thomsan's theory that atoms are soft "blobs" of matter. Most of the particles past through the gold in a straight line in his gold foil experiment. Some particles were deflected and some bounced back. -
Ernest Rutherford
He proposed that the center of an atom is a tiny,extremely dense, positively charged part called the nucleus. -
Niels Bohr
Electrons move around the nucleus in certain paths between the levels. Electrons can jump from a path in one level to a path in another level, like a ladder. -
20th century- Shrodinger & Heisenberg
Electrons dont travel in definate paths as Bohr suggested, the exact path of an electron cannot be predicted
