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Democritus discovered that all objects are made of little things that are indivisible and indistructible. He called these things "atoms". Unfortunately, he could not provide chemical evidence and many scientists doubted this theory.
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Aristotle concluded that everything is composed of matter that can only be changed by growth, decay, or motion. He also believed in the five elements fire, water, earth, air, and aether.
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Robert Hooke was working with a partner in a lab when he discovered tiny "cells" on a piece of cork. He then called these things "cells".
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Dalton was a chemist that added onto Democritus's atomic theory. In short, all elements are created from indestructable particles called atoms. All different elements have different atoms. Also, he introduced the theory of compounds, in which different elements would combine and make a new element.
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In 1859, J. Plucker built one of the first gas discharge tube.
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In 1861, William Crooke discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek thallos, a green shoot. Crookes also identified the first known sample of helium.
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The Russian chemist by the name of Dimitri Ivanovich Mendelev developed the first periodic table, which displayed the details on every chemical element.
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James Clerk Maxwell proposed electric and magnetic fields filled the void.
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E. Goldstien used a Cathode Ray Tube to study "canal rays" which had electrical and magnetic properties opposite of an electron.
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G.J. Stoney discovered that electricity was made of negative particles called electrons.
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In 1895 Wilhelm Roentgen discovered the existence of X-rays.
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In April, 1897, J.J. Thomson discovered that there are particles nearly 1000 times smaller than an atom. He called these particles "corpuscles", but they were later renamed to "electrons".
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In the year 1898 the Curie's discovered two radioactive elements, Polonium and Radium.
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In 1899, Max Planck proposed the smallest unit of time in which he called the planck.
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In the year 1900, Max Planck explained hot glowing matter. He called this the idea of Quanta.
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In 1903, Rutherford named a certain type of radiation that a French chemist discovered. He named it Gamma ray. It went along with his previous Alpha and Beta rays.
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In 1905, Albert Einstien published the equation E=mc2.
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Hans Gieger developed an electrical device used to find alpha particles and "click" when near it.
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In 1911, Ernest Rutherford came to the conclusion that the nucleus was very dense, and positively charged. He also concluded that electrons were outside the nuclus. He discovered this by using alpha particles as atomic bullets.
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In 1913, Henry Moseley created Moseley's law, which was the mathematical relationship between the wavelengths of the X-rays produced and the atomic numbers of the metals that were used as the targets in X-ray tubes.
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In 1913, Niels Bohr introduced the Bohr model, which was used to display information about atoms.
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Through mass spectrograph, Aston discovered isotopes.
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James Chadwick used alpha particles to discover a neutral atomic particles that was similar to an electron. This was called the neutron.
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Enrico Fermi conducted the first chain reaction that released energy from an atoms nucleus.
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It took place in front of 300,000 people. The airforce display team collided during their display. 67 died and 346 were injured by the plane explosion and fire.