Periodic table timeline

  • 500

    Democritus and Leucippus

    They are the first people who recorded the concept of atoms (invisible building blocks of our world). They thought that certain elements had hooks to stick together or some elements had spikes.
  • Hennig Brand

    Hennig Brand
    He discovered phosphorus by heating residues from boiled urine.
  • John Dalton

    John Dalton
    He is credited to have the first modern atomic theory in his book called A new system of chemical philosophy. Some of his experiments lead to the earliest measurements of atomic mass. He imagined atoms as small little balls that combined to make different things (and that they also had different types of atoms.
  • Dimitri Mendeleev

    He started the development of the periodic table by arranging elements by atomic mass and made room for more just in case.
  • Marie and Pierre Currie

    They both discovered the existence of Radium and Polonium
  • JJ Thompson

    JJ Thompson
    He discovered that atoms have electrons. He thought atoms were like blueberry muffins and if you split one open it would have a bunch of electrons inside of it. He thought the 'dough' of the muffin was a positively charged substance.
  • Robert Millikan

    He discovered the charge of an electron
  • Hans Gieger and Rutherford

    Hans Gieger and Rutherford
    They discovered the nucleus and that atoms were mostly empty space.
  • Niels Bohr

    Niels Bohr
    He discovered the orbit of electrons and that they had different 'layers' he thought they made an orbit like a planet around a sun.
  • Lise Meithner

    Lise Meithner
    She discovered one of the heaviest elements protactinium in 1917
  • Erwin Schrodinger

    A lot of scientists like Erwin discovered that the electrons around the nucleus weren't orbiting in a circular motion like planets around a sun, but more like flies sketching out different shapes.
  • Wolfgang Pauli

    He made the Pauli principle which states, that no two electrons in an atom could have identical sets of quantum numbers.
  • Maria Goeppert Mayer

    She published a paper about double beta decay radioactivity that happens when two protons change to two neurons. In 1938 she predicted the frequencies that a molecule would absorb and emit electromagnetic radiation. She did a lot more for elements science too. She is also one of the two women who won the noble prize for physics in 1963.
  • James Chadwick

    James Chadwick
    He discovered neutrons in the nucleus of the atom.