Historic timeline of the atom

By Jazmin_contreras
  • 400 BCE

    Democritus

    Democritus
    EXPERIMENTS USED: He discovered that the world is made up of empty space and tiny particles called atoms. CONTRIBUTIONS: Matter can be broken into infinitely smaller places.

  • John Dalton

    John Dalton
    EXPERIMENTS USED: He identified the hereditary nature of red- green color blindness. He also revealed the concept of Dalton’s Law of Partial Presures. CONTRIBUTIONS: All the matter is composed of small particles called atoms.

  • JJ Thomson

    JJ Thomson
    EXPERIMENTS USED: set out to prove that the cathode rays produced from the cathode were actually a stream of negatively charged particles called electrons. From Maxwell’s theory he knew that charged particles could b defected in a magnetic field.
    COONTRIBUTIONS : He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.

  • Ernest Rutherford

    Ernest Rutherford
    EXPERIMENTS USED : Gold Foil Experiment
    CONTRIBUTIONS: Proved the existance of a small massive center to atoms, which would later be known as the nucleus of an atom.

  • Niels Bohr

    Niels Bohr
    EXPERIMENTS USED: The discoveries of the electron and radioactivity at the end of the 19th century led to different models for the structure of the atom.
    CONTRIBUTION: Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities.