The History of The Atom

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  • History of The Atom
    • Dalton's Model
      • 1870s- One of the first developments of the atom.
      • Dalton carried experiments on how elements combined.
      • Model was a small, indestructible sphere.
      • All atoms in an element are the same.
      • Atoms in one element are different from atoms in other elements.
    • J.J Thomson
      • 1897- investigated rays given out by cathode rays.
        • Cathode rays are hot metals.
        • Cathode rays are made of particles that have less than one-thousandth of the mass of a H atom.
      • Found a particle called an electron, came from induse an atom.
      • Charge of an electron is negative.
      • Atoms have no electrical charge, they're neutral.
      • 1904- Plum pudding model.
        • Thought atoms consisted of a positive mass with negative electrons embedded.
        • Did not know what positive mass was made out of.
          • Solid/cloud
    • Rutherford
      • 1899- Some materials emit particles.
        • These were called alpha particles.
        • Alpha particles have a positive charge.
      • Decided to fire alpha particles at a piece of gold foil.
      • Geiger and Marsden helped with experiment.
      • Alpha particle source in a lead box with narrow hole.
        • Alpha particles were fired out at gold foil.
          • Some alpha particles bounced back.
            • This was because they had hit the nucleus.
      • Discovered that atoms have a nucleus.
      • Nucleus holds the mass of the atom.
        • Later scientists discovered that the mass contained protons and neutrons.
    • Bohr Model
      • 1913- Electrons can only move around fixed orbits.
        • These are electron shells.
    • Things to Remember
      • Atom is 10x10 power of - 10, standard form.
      • PEN: Protons, Electrons and Neutrons.
      • Length of a molecule: 10x 10 to the power of -8.

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