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  1. Dalton
    Dalton’s Atomic Theory:1) Matter is composed of tiny, indivisible particles called atoms*2) Atoms of the same element have the same mass and properties*3) Atoms combine in whole number ratios to form compounds4) In chemical reactions, atoms rearrange what they are attached to*Both disproved since Dalton’s time; #1 has been disproved by atomic bombs, #2 has since been disproved byisotopes
  2. JJ Thomson
    JJ Thomson’s Atomic Model – “Plum Pudding Model” Theorized that the atom is a large positively charged mass with negative electrons studded throughout. Provedwrong by Rutherford’s gold foil experiment
  3. Rutherford
    Rutherford’s Atomic ModelTheorized that the atom contained a dense highly positive center that contained most of the atom’s mass, and theelectrons were instead surrounding, rather than interspersed.
  4. Neils Bohr
    Neils Bohr’s Atomic ModelFirst to explain the atomic spectrum. He developed a new model of the atom in which electrons orbit around thenucleus. His theory included the idea of quantized energy levels, meaning the electrons must be a fixed distanceaway from the nucleus, known as an energy level.
  5. Louis de Broglie
    Louis de Broglie’s Atomic TheoryElectrons have ‘wave-particle duality’. In other words, they exhibit features of both waves and particles. They areparticles because they have a known mass, but we see their wave nature in their ability to diffract. De Broglienoted that the faster an electron moves, the more kinetic energy it has and thus the shorter its wavelength. Hetheorized the relation between wavelength and an electron’s kinetic energy: λ = h / mv where m = mass and v = velocity
  6. Werner Heisenberg
    Werner Heisenberg’s Uncertainty PrincipleThe puzzling part of de Broglie’s theory was that the velocity of an electron related to its wave nature, whereasthe mass related to its particle-like nature. This was hard to reconcile. That is, until Heisenberg’s theory. He theorized that(Δ x ) (m Δ v) > h / 4piWhere x is the position of the electron, m is its mass, and v is its velocity. This relationship between position and velocity introduced complimentarity, the notion that an electron is either a particle or a wave, never both simultaneously.

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2012-09-20 16:58:42
Chemistry History

History of Chemistry
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