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500 BCE
The Alchemists
They proved that all metals are composed of mercury and sulfur and that it's possible to changer this materials into gold.
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450 BCE
Democritus
He proposed that all matter was made up of tiny things called atoms. He has little or experiments or evidence to back up his theory.
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427 BCE
Plato
He proposed that atoms are broken down into four main elements: fire, water, air and Earth.
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Robert Boyle
Boyle helped to develop a definition for an element. He saw that all substances were made up of atoms.
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Antoine Lavoisier
He proposed the Law of Conservation of Mass. This law states that mass cannot be created or destroyed.
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John Dalton
He stated that compounds are created by combining two atoms and that atoms of given elements are identical in their mass and properties.
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Billiard Ball Model
John Dalton Created the Billiard ball model to show a visual of what an Atom looks like. -
Amedeo Avogadro
His law states that equal volumes of gasses under the same pressure have the same number of molecules.
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Pierre and Marie Curie
They discovered the strong radioactive elements known as polonium and radium. They discovered radioactivity.
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J.J. Thompson
He proposed that all atoms contain negatively charged subatomic particles or electrons.
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Plum Pudding Model
It was first proposed by J. J. Thomson.
Like negatively charged "plums" contained in a positively charged "pudding," electrons are surrounded by a volume of positive charge.
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Albert Einstein
Albert proved the existence of atoms. His atomic theory stated that any liquid is made of molecules.He developed the theory of relativity.
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Robert Millikan
He determined the charge magnitude of an electron. He proved and explained his discovery by using an oil drop experiment to find out the charge of an electron.
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Ernest Rutherford
He discovered that uranium produces two forms of radiation: alpha and beta particles.
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Neils Bohr
He proposed that outer orbits in an atom could hold more electrons than the inner orbits.
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Solar System Model
The Solar System Model is a system consisting of a small, dense nucleus surrounded by orbiting electrons created by Ernest Rutherford. www.britannica.org -
Henry G.J. Mosley
He discovered that each element contains a specific number of protons. He was also , English scientist who was Rutherford's student.
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Electron Cloud Model of the Atom
Proposed by Erwin Schrodinger it was a small but massive nucleus surrounded by a cloud of rapidly moving electrons.
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Wener Heisenberg
German Physicist who developed a mathematical way of expressing the energy levels of electrons in an atoms.
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Erwin Schrödinger
He was one of the "fathers of quantum mechanics". He created an equation that accurately calculated the energy levels of electrons in an atom.
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James Chadwick
British Physicist who was the first to demonstrate the existence of neutrons.
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