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200
Aristotle
Aristotle's atomic theory was that there are only four elements and these are earth, fire, air and water and all these elements had a kind of ‘atomos' or smallest unit which made up all the other matter which can be found on Earth. were two forces: conflict and harmony. His model included elements which move in a line to their “proper place,” where theywill be at rest. So the conflict was thought to cause bad things, and harmony good things. -
202
Democritus
Democritus stated that atoms are individually created and cannot be separated, no matter what scientific procedures are applied. The theory also says that there is no specific size that the atom has to be. It differs depending on the many factors influencing them. He also says that atoms cannot be split. His model included single atoms that were supplied with attachments: some with hooks and eyes others with balls and sockets. -
John Dalton
His theory was that all matter was made of atoms which are indivisible and indestructible. Also, that atoms in the same element have the same mass and properties. And lastly that a chemical reaction is just a chemical change. To prove this to people he made a model involving two wooden balls with holes in them. Then he placed sticks into the holes of one ball and put the two balls together to show how atoms a connected. -
Michael Faraday
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism. -
Wilhelm Roentgen
Using a CRT he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them "X-rays". -
Joseph John Thomson
J.J. Thomson was best known for discovering the electron. He was also known for his work with "cathode rays". In 1899, he measured the charge of the particles, and how they were assembled into atoms.He was then awarded the Nobel Prize for physics in 1906 for this work. His expirement included a cathode ray tube which is just an electronic device where a beam of particles were sent between a positive and negative terminal in a vacuum tube which creates a strange light. -
Hantaro Nagaoka
He was the first to present a Saturnian atomic model close to the presently accepted model. Although some of his facts were incorrect and he couldn't back up his information, his model was still pretty accurate. His model showed that the electrons orbit like Saturn’s rings around the nucleus which itself contains a positive charge. -
Ernest Rutherford
He discovered that the atom has a positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. He is also known for his famous gold foil expirement. This was where he fired radioactive particles through thin gold metal foils and detected them by using screens coated with zinc sulfide. -
Niels Bohr
Niels Bohr created a model that is well known today as the "planetary model". This is where neutrons and protons are occupying a region called the nucleus and the electrons orbit the nucleus like how the planets orbit the sun. Most of the things in his model were correct but some facts were wrong. -
Louis de Broglie
Born August 15th,1892 Louis suggested that, like and light electrons could act as both particles and waves. This was soon proven true in experiments that showed how electron beams could be bent as they passed through a slit like light could. Then the waves produced by an electron in its orbit around the nucleus sets up a standing wave of a precise wavelength, energy, and frequency like how guitar string set up a standing wave when strummed. -
Ernest Marsden
Ernest worked closely with Ernest Rutherford and helped to create the gold foil expirement. He was to observe a tiny fraction of alpha particles that were fired at a gold foil which were deflected straight back. He and Rutherford used this result to determine a new structure of the atom, with most of its mass concentratedon a central nucleus. -
Erwin Schrodinger
Born August 12th, 1887, Erwin sayed that electrons act in a wave-like way rather than just as particles and that their exact location in an orbit could not be calculated correctly, almost like a cloud. . His view of the atom can be seen as "layers within layers" in terms of the electron shell. His modle was called the cloud model which invloved red dot in the middle of a cloud which represents the nucleus while red dots around the outside of the cloud represent an instance of the electron. -
James Chadwick
James discovered a third type of subatomic particle, which he then named the neutron. Neutrons help to stabilize the protons in the atom's nucleus. Because the nucleus is so tightly packed together, the positively charged protons would repel against each other normally. But electrons don't have any electrical charge therefor they are electrically neutral. He proved this by using a sample of Beryllium with alpha particles in them which causes it to emit a weird radiation. -
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