1. Democritus
    • A greek philosopher named Democritus came up with the nept o atom.
    • Small, hard particles that could not be divided.
    • Democritus said that all atoms are always moving.
  2. John Dalton
    • All substances are made of atoms. Atoms are small prticles that cannot be created, divided, or destroyed.
    • Atoms of the same element are exactly alike, and atoms of different elements are different.
    • Atoms join with other atoms to make new substances
  3. J.J. Thomson- found electrons
    • Thomson experimented with a cathode-Ray Tube.
    • Thomson called the negatively charged particles coupuscles.
    • We now call these negatively charged particles electrons.
    • Thomsons Plum Pudding Model.
    • His plum Piddung model showed a possible structure of the atom with the negative charges.
  4. Ernest Rutherford
    • Rutherford discoerved athat the atom had a small, dense nucleus than contained positive charges.
    • Gold foil expirement- aimed charged particles at a thin sheet of gold foil.
    • Trying to see where the positive particles would go.
    • A particle that actually hit the nucleus would be delfected almost straight back.
  5. Rutherfofords Planetary Model
    • The atom is mostly empty space through which electrons travel.
    • The atom has a small, dense, poisively harged nucleus. (Most of the mass is in the nucleus).
    • Electrons travel around the nucleus like planets around the sun.
  6. Niels Bohr
    • In 1913, Niels Bohr determined that electrons traveled around the nucleus in definite paths.
    • He also discovered that electrons could jump from a path in one level to a pth in another level.
  7. Heisenber/Schrodinger
    • Schrodinger and Heisenberg explained that electrons do not travel in definite paths.
    • electron paths cannot be predicted.
    • The current theory suggests that electrons are found in regions called electron clouds.
Card Set
Note-Cards for 2.1