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400
Democritus
"HISTORY OF THE ATOM FROM DEMOCRITUS TO BOHR AND SCHRÖDINGER." HISTORY OF THE ATOM FROM DEMOCRITUS TO BOHR AND SCHRÖDINGER. Web. 25 Feb. 2014.Democritus was a Greek philosopher who discovered the atom in 400 BC.He stated that atoms were small, hard particles and were made of the same material but were different shapes and sizes. Democritus used a theory that stated "Matter could not be divided into smaller and smaller pieces forever. Eventually, the smallest possible piece would be obtained. This piece would be indivisible." He thought the atom looked like a sphere. -
400
Aristotle
"Aristotle (384-322 B.C.E.)." Aristotle. Web. 25 Feb. 2014.Aristotle promoted the idea that the universe was made from earth, air, fire, and water in 400 B.C.. Aristotle developed logic called Aristotle logic which he used to make this discovery. His model shows the four elements the universe is made of. -
Period: 400 to
History of the Atom
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Dalton
"Dalton Atomic Theory." Dalton Atomic Theory. Web. 25 Feb. 2014.John Dalton discovered the atom in 1803. He discovered that elements were made of the smallest particles called atoms. He also found that all atoms for one element are identical. He also said that different elements could combine in a chemical reaction.Dalton had a theory that said "All matter is composed of atoms. Atoms cannot be made or destroyed. All atoms of the same element are identical. Different elements have different types of atoms." Dalton also believed the atom looked like a sphere. -
Thomson
"Joseph John Thomson." Homepage of the Chemical Heritage Foundation. Web. 25 Feb. 2014.In 1897, Thomson discovered the electron.He said that electrons are positioned by electrostatic forces. Thomson used an experiment called the "Cathode Tube Experiment". To discover the electron. The name for his model is "The Plum Pudding." His model looked like a sphere filled with electrons. -
Rutherford
"The Rutherford Experiment." The Rutherford Experiment. Web. 26 Feb. 2014.In 1917, Rutherford did the "Gold Foil Experiment." During this experiment, Rutherford was able to split an atom. During the process, he discovered the proton. His experiment is called the "Gold Foil Experiment" His model displays a picture of an atom with a nucleus and electrons. -
Bohr
"Niels Bohr." Niels Bohr. Web. 27 Feb. 2014.In 1913, Neils Bohr proposed of what he thought looked like a hydrogen atom. In order to do this, he took what he knew from previous scientists and did numerous experiments on hydrogen.He also thought the electron traveled around the nucleus in a circular orbit. His model looks like a nucleues with electron rings surrounding it. -
Schrodinger
"Development of the Atomic Theory." Development of the Atomic Theory. Web. 26 Feb. 2014.Schodinger developed the atomic theory in 1926. The theory predicts the odds of the location of the electron. He used mathematical equations to describe the likelihood of finding an electron in a certain position. His model is called the "Quatum Mechanical Model".
