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Period: 200 to
Development of the Atomic Theory
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440
Democritus 440 B.C.
Democritus was a Greek philosopher and he explained that if you were going to cut a piece again and again to it smallets core then it could not be cut. That explained that this was an atom. He stated that all atoms were small hard particles. -
500
Aristotle 500 B.C.
Aristotle is a Greek philosopher who disagreed with Democritus's ideas. He thought that there could not ever be a particle that could not be cut; even if it is at its smallest core. He had such a strong influence on people that no one challenged him and he was right but he would be terribly wrong. -
John Dalton
He stated that all substances are made up of atoms. Atoms are small particles that cannot be created, divided, or destroyed. Another theory he stated is that atoms of the same element are exactly alike, and atoms of different elements are diffrent, Finally ,the last thing he stated in his atomic theory was that atoms join with other atoms to make new substances. Most of Dalton's theory was mostly correct but later in the 1800's many scientist fond flaws in his theory. -
J.J. Thomson
J.J. Thomson found a flaw in Dalton's theory. He stated that atoms had smaller particales inside them. This means that atoms can be broken into even smaller parts. He discovered that the positive part of an atom is the proton and the electric particle is the electron. -
Ernest Rutherford
He was a former student of J.J. Thomson and found new directions on how atoms were arranged. He tested Thomson's theory by aiming a beam of positive particles to a thin gold sheet which was in front of the foil. He found that most of the atoms were going through but some were deflected and that was the surprise. Scientist thought that in the experiment the particles would pass right on threw but they were wrong from Rutherford's discovery. -
Ernest Rutherford
In 1911, Rutherford revised the atomic theory. He propesed a new model of the atom. He stated that the atom has a nucleus which has protons and nuetrons compacted together. If any particle went right at the nucleus then it would be pushed back the exact direction it came from. -
Niels Bohr
Niels Bohr is a Danish Scientist who worked with Rutherford on the way atoms react to light. He stated that electron's move around the nucleus in diffrent paths or energy levels. Borh's theory also stated that there is no paths between the levels but electrons can jump from one level to a another level. This theory was a valuable tool for the atomic theory but there was still room for vast improvment. -
Erwin Schrodinger and Werner Heisenberg
Erwin Schrodinger was a Austrailian physicist and Werner Heisenber was a German physicist. They both explained the nature of electrons in the atom. For example, electrons do not travel in definete paths which was a flaw on Bohrs theory. Electrons do not travel in exact paths but electrons can be found in the electron cloud. The electron cloud is estimated around the nuclues.
