Atomic structyre

The Historty of Atomic Theory

  • 500

    ANCIENT GREEKS - Empedocles 450BC

    Suggests that all matter was made from combinations of fire, air, water and earth
  • 500

    ANCIENT GREEKS - Democritus 47BC - 40BC

    Proposed that if a sample of matter was cut into smaller and smaller pieces, they would eventually become indivisible. He named them atoms
  • 500

    ANCIENT GREEKS - Aristotle 384BC-322BC

    Matter is continuous and infinitely divisible. Supported Empedocles theory. Said that you could change one material into another by varying the proportions of earth, air, fire and water.
  • Period: 500 to

    History of Atomic Theory


    • Proposed that all matter consisted of tiny particles called atoms
    • Atoms could not be divided into smaller particles
    • Atoms of the same element were alike
    • Atoms combined in simple whole number ratios
    • Atoms from each element are different and combine to make other substances

    • Discovered the electron which proved that atoms were not indivisible
    • Proposed that atoms were positively charged spheres with negatively charged particles (electrons) embedded in them (the plum pudding model)

    • Proposed a nuclear model for the atom
    • Discovered the nucleus by bombarding a thin gold foil with positively charged particles which were reflected off 1 out of every 10000
    • The nucleus was where the positively charged atoms were and was where most of the mass was
    • The nucleus had electrons orbiting on energy shells however he proposed that they would eventually spiral in toward the nucleus.

    • Modified Rutherford’s model and proposed that the electrons orbit the nucleus on different energy levels
    • Proposed that electrons have different amounts of energy which is why they existed at different levels
    • Electrons could move energy levels by gaining or losing energy

    • Discover the neutrons in the nucleus
    • Found that they had no electric charge and the same mass as the proton