development of the periodic timetable

  • Discovery of phosphorus

    Hennig Brand tried to create an object that could turn metals into gold.
  • hosphorus became public.

    Robert Boyle also discovered phosphorus, and it became public.
  • Johann Dobreiner

    Johann Dobereiner grouped similar elements, this was the start of teh periodic table.
  • 47 elements

    at lease 47 elements were discovered, and scientists started to see patterns in the characteristics
  • Law of the triads

    Middle element in the triad had atomic weight that was the average of the other two members- this was the law of the triads
  • John Newlands

    In 1863 English chemist John Newlands divided the than discovered 56 elements into 11 groups, based on characteristics.
  • Law of Octaves

    he wrote a paper proposing the Law of Octaves which was elements exhibit similar behavior to the eighth element following it in the table.
  • Dimitri Mendeleev

    dimitri mendeleev arranged chemical elements by atomic mass. he also predicted the discovery of other elements, and left spaces open in his periodic table for them.
  • Elements by atomic weights

    dimitri then arranged elements by atomic weights and properties. Mendeleev's periodic table of 1869 contained 17 columns with two periods of seven elements each followed by two nearly complete periods.
  • Radioactivity

    Antoine Bequerel first discovered radioactivity. three types of radiation; alpha, beta and gamma rays.
    Marie and Pierre Curie started working on the radiation of uranium and thorium, which lead to the discoverey of radium and polonium. They discovered that beta particles were negatively charged.
  • Henry Moseley

    He performed x-rays on know elements. he was able to see relationships between them
  • Noble gases

    In 1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0.
  • Discoverey of electrons

    J. J. Thomson first discovered electrons. John Townsend and Robert Millikan determined their exact charge and mass.
  • 1990

    Bequerel discovered that electrons and beta particles which were identified by the Curies are the same thing.
  • Break down of atoms

    Rutherford announced that radioactivity is caused by the breakdown of atoms.
  • Nobel Prize

    In 1906, Mendeleev came within one vote of receiving the Nobel Prize in chemistry.
  • Electrons orbit

    Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom.
  • Orbital

    Bohr discovered that electrons move around a nucleus in energy called orbitals. Radiation is emitted during movement from one orbital to another.
  • Protons in the atomic nucleus

    Rutherford first identified protons in the atomic nucleus. English physicist Henry Moseley provided atomic numbers, based on the number of electrons in an atom, rather than based on atomic mass.
  • Lanthanides and actinides

    Glenn Seaborg identified lanthanides and actinides, which are usually placed below the periodic table.
  • Neutrons and Isotopes

    James Chadwick first discovered neutrons, and isotopes were identified.
    In that same year Cockroft and the Walton first split an atom by bombarding lithium in a particle accelerator, changing it to two helium nuclei.
  • 60 elements

    By 1860 about 60 elements were known.