Atomic Theory BY Kristina Cvijanovic

By PMurphy
  • 400

    492 BC - Democritus' Discovery

    Democritus proposed that matter is made up of small indescructable things called atoms. He used 'atomos' when talking about them, which means 'uncuttable'
  • 400

    332 BCE - Aristotle's Dicovery

    Unlike Democritus, Aristotle thought that all matter was made up of 4 elements; fire, water, earth, and air. He also proposed that Earth was in the center of the universe, a popular beleif back then.
  • Period: 400 to

    Atomic Theorys - Kristina Cvijanovic

  • 1800 - John Ddalton's Dicovery

    John Dalton transformed Democritis' ideas into a modern atomic model. His theory was that all matter was made of tiny microscopic particles called atoms. He also thought that atoms of different elements combine in small, whole number ratios to form compunds.

  • 1897 - J. J. Thomson's Dicovery

    J.J. Thomson discovered the electron. He also conducted the Cathode Ray experiment. By adding an electric charge, he found that the moving peices were opposite. He also made the Plum Pudding model.

  • 1909 - Robert Millikan's Discovery

    Robert Millikan determined the amount and charge in an electron. He conducted the Oil-Drop experiment by measuring the effect of an electric field on very small oil droplets.

  • 1912 - Ernest Rutherford's Dicovery

    Ernest Rutherford discovered the Nucleus. He was also the one to conduct the gold foil experiment.

  • 1913 - Neils Bohr

    Neils Bohr proposed that an electron is found only in specific circular paths, or orbits, arounf the nucleus.

  • 1932 - Sir James Chadwick

    Sir James Chadwick comfirmed the existence of the nuetron in the nucleus. He thought that the atom was motly empty space.