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(NOTE:This is 400 B.C)
Aristotle believes all things are made of fire, air, earth, and water. There were two forces, conflict and harmony. He also believed there was a fifth element aither which made up the heavens. -
(NOTE: This is 460B.C.)
Democritus claimed everything is made up of basic matter particles called atoms, or atomos on Greek. -
John Dalton studied and experimented with elements to create his atomic theory:
-All matter is made of atoms. Atoms are indivisible and indestructible.
-All atoms of a given element are identical in mass and properties
-Compounds are formed by a combination of two or more different kinds of atoms.
-A chemical reaction is a rearrangement of atoms. -
Döbereiner discovered trends of certain properties in groups of elememnts
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Newlands was the first person to arrange the periodic table of elements by their atomic weights
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Mendeleev created the first periodic table with the 63 known elements arranged by atomic mass and properties. He even correctly predicted two yet to be discovered elements.
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He noticed that when the elements are arranged in the order of their atomic weights they fall into groups that share similar chemical and physical properties. He also made a plot comparing atomic volume and weight.
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Crooke developed the Crooke's tube. From that, he later developed the cathode ray tube that used a stream of free electrons.
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Planck discovered the quantum of action, (Planck's constant h) explaining the pattern of light intensity emitted from a black body at any given frequency
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Becquerel discovered x-ray like radiation from some phosphorescent materials when illuminated by sunlight. This is known today as radiation
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This is the "plum pudding" atomic model J.J.Thomson proposed after discovering the electron
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Rutherford discovered, by firing radioactive particles through gold foil, that atoms have a centeral positive nucleus with negativley charged electrons orbiting the nucleus.
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Bohr establishes that electrons travel in stationary orbits, this led to the calculation of energy levels and the development of the solar system atomic model.
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Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This is known as quantum mechanics.
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Dolly the sheep, the first the first mammal to be successfully cloned from an adult cell, is born.
