TIMELINE OF THE PERIODIC TABLE

By Alondra Figueroa
  • 492 BCE

    DEMOCRATUS

    DEMOCRATUS
    Everything is composed of tiny particles called atoms, that come together to build something. All atoms are invisible but alike. Experimented on plants and minerals.

  • JOHN DALTON

    JOHN DALTON
    He proved that all matter has atoms being undivisible and indestructible. Compounds having 2 or more chemical things together.

  • JJ THOMSON

    JJ THOMSON
    Discovered electrons. Discovered the method of separating atoms & molecules with a later on also developed by Ashton, Dempter the discovery of Isotope. Tried to find the charge to mass ratio. Experimented on changing particles.

  • ERNEST RUTHERFORD

    ERNEST RUTHERFORD
    Father of the nuclear physics. Used the 2 types of radiation to find total mass of an atom. He would use different types of elements at a time to find results and compare them. He would experiment firing alpha particles at foil. His professor made him look into the nuclear stuff. In 1919 he also introduced the nuclear reaction.

  • NIELS BOHR

    NIELS BOHR
    Developed the Bohr model for the atom. Discovered electrons orbiting around the nucleus. Using Rutherford's theory of the atoms' way of orbiting & positive charges & negative.

  • SCHROEDINGER HEIERBERG

    SCHROEDINGER HEIERBERG
    Formulated the quantum theory. He tried to find the energy for each atom. He found the neutron and proton model in the nucleus.