Development of the periodic table

By willija
  • Discovery of phosphorus.

    Discovery of phosphorus.
    Hennig Brand attempted to created a Philosopher’s Stone; an object that could turn metals into gold. He heated residues from boiled urine, and a liquid dropped out and burst into flames. This was the first discovery of phosphorus.
  • hosphorus became public.

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

    The development of the periodic table begins with German chemist Johann Dobereiner (1780-1849) who grouped elements based on similarities.
  • 47 elements

    In 1809 at least 47 elements were discovered, and scientists began to see patterns in the characteristics.
  • Law of the triads

    Law of the triads
    Dobereiner proposed the Law of Triads: Middle element in the triad had atomic weight that was the average of the other two members.
  • John Newlands

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

    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
    Dimitri Mendeleev started the development of the periodic table. He arranged chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them.
  • Elements by atomic weights

    Elements by atomic weights
    Then in 1869, Russian chemist Dimitri Mendeleev proposed arranging 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. Ernest Rutherford named 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

    Henry Moseley
    He performed x-rays on know elements. He was able to see the realtionship between x-ray frequency and number of protons.
    When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the gaps in Mendeleev's table were taken out. The modern periodic table is based on Moseley's Periodic Law.
  • Noble gases

    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

    Discoverey of electrons
    J. J. Thomson first discovered electrons. John Townsend and Robert Millikan determined their exact charge and mass.
  • Electrons and beta particles

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

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

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

    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

    Protons in the atomic nucleus
    Rutherford first identified protons in the atomic nucleus. He also transmutated (an act that changes the form or character or substance of something) a nitrogen atom into an oxygen atom for the first time. English physicist Henry Moseley provided atomic numbers, based on the number of electrons in an atom, rather than based on atomic mass.
  • Neutrons and Isotopes

    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.
  • Lanthanides and actinides

    Lanthanides and actinides
    Glenn Seaborg identified lanthanides and actinides, which are usually placed below the periodic table.
  • 60 elements

    By 1860 about 60 elements were known.