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And Now, Let’s Talk About Dead Guys
Famous Scientists who have made contributions to our understanding of Chemistry
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Democritus ~400 BC Matter could be subdivided
Broken into little spheres he called “atomos”
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Aristotle Taught Democritus Reject his theory and banished him
Matter is infinitely divisible He alone set atomic theory back
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John Dalton Englishman 1766 – 1844 Was colorblind
Based on his research, colorblindness was called “Daltonism” for a long time Dalton’s Law (gases) Atomic Theory
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Dalton’s Atomic Theory (Atom is like a billiard ball)
All elements are composed of very small particles called atoms which are indivisible.* All atoms of the same element are identical.* Atoms of different elements are different. Atoms of different elements combine in whole number ratios to form compounds
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J.J. Thomson 1856 - 1940 Cathode Ray Tube Experiment
Discovered the electron Won the Nobel Prize in Physics in 1906
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J.J. Thomson Watch the stream of “light” respond to the magnet
Like charges repel Opposite charges attract Therefore, these rays were made of negatively charged particles
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J.J. Thomson 1856 - 1940 Cathode Ray Tube Experiment
Discovered the electron Like Charges Repel/Opposites attract Electrons are negative
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Ernest Rutherford 1871 – 1937 Worked in Thomson’s lab at Cambridge
Gold Foil Experiment Won the Nobel Prize in Chemistry in 1908
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Ernest Rutherford Fired alpha particles at gold foil to see what happened Deduced that most of the atom is empty space Deduced that in the center is a densely clustered, positively charged nucleus
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Niels Bohr 1885 – 1962 Won the Nobel Prize in Physics in 1922
Planetary Model of the Atom
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Niels Bohr 1885 – 1962 Won the Nobel Prize in Physics in 1922
Planetary Model of the Atom
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Robert Millikan 1868 – 1953 The Oil Drop Experiment
Determined the amount of electrical charge of 1 electron
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Dimitri Mendeleev 1834 – 1907 Organized the first Periodic Table
Organized his table by atomic mass Left spaces for elements he expected to fit Predicted Eka- aluminum – gallium with a mass of around 68 and density of 6.0 g/cm3
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Henry Moseley 1887 – 1915 Did work bombarding samples with X- rays to analyze the number of protons in an element Now the chart is organized based on proton number not just on trends
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Other Contributors Antoinne Lavoisier- “Father of Chemistry” and the Law of Conservation of matter James Chadwick – Discovered the neutron Max Planck – The Quantum Mechanical Model of the atom.
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