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460 B.C
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Democritus discovered that all atoms are indvisible, exactly alike, and all matter is made up of atoms. Atoms cannot be destroyed only changed.
460 B.C.
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Egypt revolts against Persian rule.
460 B.C.
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Conflicts arise between the Roman patricians and plebians.
1803
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John Dalton pictures atoms as tiny, indestructible particles, with no internal structure.
1803
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Great fire in Bombay, India.
1803
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Ohio becomes the 17th state.
1808
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Anthracite coal is first burned as fuel, experimentally, in Wilkes-Barre, Pa.
1808
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According to Dalton, matter is made up of tiny particles called atoms. The atom is the smallest particle of matter that takes part in a chemical reaction. Atoms are indivisible and cannot be created or destroyed.
1808
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Congress prohibits importation of slaves.
1897
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1st British bus service opens.
1897
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World's 1st car dealer opens in London.
1897
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J.J. Thomson, a British scientist, discovers the electron. He pictures electrons embedded in a sphere of positive electrical charges.
1900
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Solar eclipse occurs.
1900
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Goldstein said that atoms contain positively charged particles called protons. Since atoms contain negatively charged particles, they must contain positively charged particles for them to be electrically neutral.
1900
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Hawaii became a US territory.
1904
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First airplane flight lasts more than five minutes.
1904
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Nagaoka suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn.
1904
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Third modern Olympic Games opens in St. Louis.
1910
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US forbid immigration to criminals, anarchists, paupers, and the sick.
1910
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Provided a value for the eletronic charge.
1910
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Portugal becomes a repubic.
1911
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First photo in US taken from an airplane in San Diego.
1911
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First public elevator in London's Earl;s Court Metro Station.
1911
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Rutherford finds that an atom has a small, dense, positively charged nucleus. Electrons move around the nucleus.
1913
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In Bohr's model, the electron moves in aircular orbit at fixed distances from the nucleus.
1913
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The USA introduces income tax.
1913
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First US paved coast to coast highway, the Lincold highway is dedicated.
1923
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De Broglie proposes that moving particles like electrons have some properties of waves. Within a few years, experimental evidence suppports the idea.
1923
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Disney company is founded.
1923
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Union of Socialist Soviet Republics is established.
1926
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Lebanon adopts constitution.
1926
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National Geographic takes 1st natural-color undersea photos.
1926
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Erwin Schrodinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model.
1932
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James Chadwick, an English physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.
1932
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US federal gas tax enacted.
1932
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World War 2: Japan occupies Harbin, China.