• elements

    In 1809 at least 47 elements were discovered
  • elements

    1863 English chemist John Newlands divided the than discovered 56 elements into 11 groups
  • periodic table

    1869 Russian chemist Dimitri Mendeleev started the development of the periodic table
  • nobal gasses

    1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases
  • atoms

    In 1903 Rutherford announced that radioactivity is caused by the breakdown of atoms.
  • protons

    1914 Rutherford first identified protons in the atomic nucleus