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One of the first atomic theorists was Democritus, a Greek philosopher who lived in the fifth century BC. Democritus knew that if a stone was divided in half, the two halves would have essentially the same properties as the whole.Therefore, he reasoned that if the stone were to be continually cut into smaller and smaller pieces then; at some point, there would be a piece which would be so small as to be indivisible. He called these small pieces of matter "atomos," the Greek word for indivisible.
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Aristotle did not believe in the atomic theory and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter. Aristotle's view was finally proven incorrect and his teachings are not present in the modern view of the atom.
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Isaac Newton theorized a mechanical universe with small, solid masses in motion.
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John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.
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Michael Faraday developed the two laws of electrochemistry.
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built one of the first cathode-ray tubes.
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built one of the first cathode-ray tubes.
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created the periodic table.
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created the periodic table
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proposed the theory of electromagnetism and made the connection between light and electromagnetic waves.
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proposed the theory of electromagnetism and made the connection between light and electromagnetic waves.
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theorized that electricity was comprised of negative particles he called electrons.
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theorized that electricity was comprised of negative particles he called electrons.
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experiments with cathode-ray tubes led him to confirm the work of earlier scientists by definitively demonstrating that cathode-rays have a negative charge.
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experiments with cathode-ray tubes led him to confirm the work of earlier scientists by definitively demonstrating that cathode-rays have a negative charge.
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discovered canal rays, which have a positive charge equal to an electron.
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discovered canal rays, which have a positive charge equal to an electron.
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discovered x-rays.
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discovered x-rays.
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discovered radiation by studying the effects of x-rays on photographic film.
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discovered radiation by studying the effects of x-rays on photographic film.
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determined the charge to mass ratio of electrons.
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determined the charge to mass ratio of electrons.
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discovered alpha, beta, and gamma rays in radiation
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discovered alpha, beta, and gamma rays in radiation.
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discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium.
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discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium.
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proposed the idea of quantization to explain how a hot, glowing object emitted light.
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came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.
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proposed the idea of quantization to explain how a hot, glowing object emitted light.
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came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.
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proposed an atomic model called the Saturnian Model to describe the structure of an atom.
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proposed an atomic model called the Saturnian Model to describe the structure of an atom.
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found that inert gases have a “stable electron configuration.”
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found that inert gases have a “stable electron configuration.”
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invented a device that could detect alpha particles.
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invented a device that could detect alpha particles.
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discovered that the number of protons in an element determines its atomic number.
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discovered that the number of protons in an element determines its atomic number.
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used a mass spectrograph to identify 212 isotopes.
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used a mass spectrograph to identify 212 isotopes.
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proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.
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proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.
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proposed that electrons have a wave/particle duality.
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created the first nuclear reaction, producing alpha particles
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proposed the existence of anti-particles.
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discovered neutrons, particles whose mass was close to that of a proton.
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discovered nuclear fission.
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discovered eight transuranium elements.
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created the first man-made nuclear reactor.