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Period: 350 to
Atomic Theory timespan
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400
Democritus - B.C.
He believed that atoms were the building blocks to all things. He also had ideas of how atoms might have looked; white things were composed of smooth atoms while black things were made of rough atoms. Also that sweet things are made of spherical atoms, and bitter things are ridged. Also thought that how solid a shape was related to how packed atoms were. -
400
Aristotle - B.C.
He was against the ideas of Democritus and believed that life couldn’t be made of small atoms because they would fall. He stated that life was made of four qualities; heat, cold, wetness, dryness. His ideas were accepted over Democritus for centuries. -
Oct 12, 1492
America was founded
America was discovered in 1492 by Christopher Columbus -
Microscopes
The first compound microscope was made in 1590 in The Netherlands -
George Washington was President
April 30, 1789 -
Joseph Proust
He came up with the law that says compounds form in definite proportions with their elements. His idea took time before it was accepted. -
John Dalton
Posed the atomic theory and the three parts. (1) All matter is made up of small indivisible particles called atoms. (2) Atoms the same element share characteristics like mass. (3) Three types of atoms: elements, compound, and complex molecules. -
Creation of the periodic table by atomic mass
Dmitri Mendeleev created the first periodic table according to atomic mass in 1869. -
Albert Einstein
Born: 14 March 1879 -
Henri Becquerel
He presented in a meeting that the special rays that are from uranium cause gas to become ionized. He stated how they differed from x-rays in the way they could be deflective by a magnetic field. -
J.J. Thomson
He conducted experiments on cathode rays that lead to the discovery of the electron that was negatively charged. -
Max Planck
Found that electrons that are bound to and atom have limitations on its energy level where as if it is unbound, it has no limit to the energy it can have. -
Robert Millikan
He was able to measure the charge of the electrons by using the findings of J.J. Thomson and his oil drop experiment. -
Ernest Rutherford 1911
He had the idea that negatively changed electrons orbited a positively changed nucleus. Also in 1920 he had the idea of neutrons -
Periodic table ordered by atomic number
Henry Moseley was the first to order the elements by atomic number so elements would fit together in groups/families and periods better in 1913. -
World War I
July 28th, 1914 -
Neils Bohr
Established the model that the negatively charged electrons orbit around the nucleus. -
Louis de Broglie
He questioned if electrons moved in waves. This suggestion of movement in waves was raised in his doctoral thesis Recherches sur la theorie des quanta. -
Erwin Schrodinger
He was give credit for finding the electron around the nucleus, even though it was not exact. Also he contributed to wave mechanics. -
Werner Heisenberg
He published his uncertainty principle; he could find the probable position of an electron and its momentum. This helped launch quantum mechanic model. -
Electron Microscopes
The first Transmission Electron Microscope (TEM) was made in 1931 by Max Knoll and Ernst Ruska -
James Chadwick
He established that atomic number is determined by the number of protons. He also discovered that in the nucleus had not only protons, but also the neutrons. -
World War II
German invasion of Poland on September 1, 1939 -
Nuclear bomb tested
The first nuclear bomb was tested by the United States on July 16, 1945
