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Development of the Periodic Table

  • Period: to


    All dates have been given to 1st January unless a more accurate date is known.
  • Dalton's Atomic Theory

    Dalton's Atomic Theory
    John dalton proposed that all matter is made from tiny particles called atoms
  • Triads

    In 1829, Johann Dobereiner started the work that led to his theory of triads. This had him showing that certain groups of 3 elements showed trends in a variety of properties. It worked for Lithium, sodium and potassium, Chlorine , Bromine and Iodine, and a few other sets of elements.
  • Octaves

    John Newlands was the first chemist to come up with a table of the elements. He noticed that several properties repeated every eight elements, if they were ordered by atomic weight. He called this the law of octaves. However this only worked for the first few elments, and people did not believe him.
  • Periodic table

    Periodic table
    In 1869, Dmitri Mendeleev pubkished his periodic ttable of all the known elements. He ordered them by atomic weight and suggested that properities repeat periodically. He also left gaps for elements that had not been discovered yet, which was controversial. he also predicted properties for these elements.
  • Gallium Discovered

    Gallium Discovered
    Mendeleev's Ekaaluminium discovered thsi year
  • Scandium Discovered

    Scandium Discovered
    Mendeleev's Ekaboron discovered this year
  • Germanium Discovered

    Germanium Discovered
    Mendeleev's EkaSilcon discovered this year
  • Discovery of the electron

    Discovery of the electron
    J J Thompson discovered that a negatively charged particle of low mass existed. It was called the electron.
  • The nucleus is discovered

    The nucleus is discovered
    Ernest Ruttherford and his team discovered that atoms have a small, dense region at their centre called the nucleus.
  • Shells discovered

    Shells discovered
    Niels Bohr first proposed that electrons orbit the nucleus in fixed shells.