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The Persian empire became the biggest empire in the world and the Stone-Hurling Catapult was invented.
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In 400 BC Democritus theorized that all material bodies comprise indivisibly small “atoms".
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The timeline of change in the model of an atom and discoveries about the atom.
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John Dalton theorized that the atoms within a given element are all the same size and weight, but the atoms of different elements are different from one another. He defined an atom to be a ball-like structure. "Marble Model" -
The Louisiana Purchase encompassed 530,000,000 acres of territory in North America that the United States purchased from France in 1803 for $15 million.
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Michael Faraday discovered that Atoms had to do with electronic charge, not knowing how or why.
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Goldstein discovered evidence for the existence of a positively charged particle inside an atom.
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Thomson said that atoms contain tiny negatively charged subatomic particles or electrons. In Thomson's plum pudding model of the atom, the negative electrons were embedded in a uniform sphere of positive charge. "Plum Pudding" Model. -
Theodore Roosevelt became president of the United States of America.
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In 1910, Robert Millikan determined the magnitude of the electron's charge using oil, discovering the charge of an individual electron.
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Rutherford discovered the atomic nucleus and developed a model of the atom that was similar to the solar system. Like planets, electrons orbited a central, sun-like nucleus. Discovered the proton, didn't know about the neutron yet. Referred to as the “nuclear” model, “Jimmy Neutron” model. -
The sinking of the Titanic dominated headlines in 1912. -
Neils Bohr created a diagram of the atom depicting a small nucleus and electrons circling around it in a fixed consistent orbit. “Solar system” model. -
On August 18 1920 the Nineteenth Amendment was passed, giving women the right to vote.
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Tennessee schoolteacher John T. Scopes is arrested for teaching the theory of evolution, forbidden by state law.
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Schroedinger's model consisted of a dense nucleus surrounded by a cloud of electrons at various orbital levels. "Electron Cloud" model. -
Werner Heisenberg formulated a type of quantum mechanics based on matrices and proposed the uncertainty principle, the position and how fast a particle is going cannot be known exactly.
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As stocks continued to fall during the early 1930s, businesses failed, and unemployment rose. In 1932 one of every four workers was unemployed.
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In May 1932, James Chadwick announced that the core of an atom also contained a new uncharged particle which he called the neutron. Referred to as the “electron cloud” model with neutrons added.