-
Jan 1, 1001
400 BC- Democritus
Democritus was a Greek philosopher that believed that you could keep cutting something in half until you ended up with a small had particle that could not be cut in half. He would call this particle an atom which comes from the Greek word atomos which means not able to be divided. -
Jan 1, 1001
382 BC- Aristotle
Aristotle was another Greek philosopher that disagreed with Democritus. Aristotle believed that you would end up with an object that could not be cut and he had such a great influence on the people that nobody believed Democritus even though he was right. -
John Dalton
John Dalton was a scientist that came up with his atomic theory in 1803. His atomic theory stated that all substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed. It also stated that atoms of the same element are exactly alike, and atoms of different elements are different. Finally his law stated that atoms join with other atoms to make new substaelements are different. Finally his law stated that atoms join with other atoms to make new substances. -
J. J. Thomason
J. J. Thomason was a British scientist that found that there was a mistake in Dalton's theory. He discovered that there are smaller particles inside the atom which means that the atom could be divided into even smaller pieces. He also experimented with a cathode- ray tube. He concluded that negative particles are attracted to positive particles. He also discovered that all atoms have negatively charged particles and there are called electrons. -
Ernest Rutherford
Ernest Rutherford a former student of Thomason designed an experiment and studied the parts of the atom. He took a beam of positively charged particles and aimed it at a thin sheet of gold foil. This experiment concluded that atoms were mostly empty space with a tiny part of dense matter. -
Ernest Rutherford
In 1911 Ernest Rutherford revised the atomic theory that Thomason had made a new model of the atom. He proposed that the atom had a very small dense center and that the center of the atom was 100,000 times smaller than the atom its self. -
Niels Bohr
In 1913 a scientist name Niels Bohr who worked with Rutherford studied the way atoms react with light. These experiments led him to propose a new atom model which said that the levels in which the electrons travel around the nucleus. The levels are like ladder rungs, you can go on the ladder rungs but you cannot go in between the ladder rungs. -
Schrodinger and Heisenberg
Erwin Schrodinger and Werner Heisenberg explained how electrons and they gave us the model of what the atom looks like today. They said that the electrons had no set pattern of where they traveled but you could most likely find them in electron clouds around the nucleus.
