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Philostone
German merchant and amateur alchemist Hennig Brand attempted to created a Philosopher’s Stone; an object that supposedly could turn metals into pure gold. He heated residues from boiled urine, and a liquid dropped out and burst into flames. This was the first discovery of phosphorus. -
Robert Boyle
Robert Boyle also discovered phosphorus, and it became public. -
Antoine Lavoisier
Antoine Lavoisier grouped the elements based on their properties into gases, non-metals, metals and earths. Several other attempts were made to group elements together over the coming decades. -
Elements
At least 47 elements were discovered, and scientists began to see patterns in the characteristics. -
Johann Döbereiner
Johann Döbereiner recognised triads of elements with chemically similar properties, such as lithium, sodium and potassium, and showed that the properties of the middle element could be predicted from the properties of the other two. -
Karlsruhe, Germany
It was not until a more accurate list of the atomic mass of the elements became available at a conference in Karlsruhe, Germany in 1860 that real progress was made towards the discovery of the modern periodic table. -
Alexandre Béguyer de Chancourtois
Alexandre Béguyer de Chancourtois was a geologist, but this was at a time when scientists specialised much less than they do today. His principal contribution to chemistry was the 'vis tellurique', a three dimensional arrangement of the elements constituting an early form of the periodic classification. -
John Newlands
John Newlands divided the than discovered 56 elements into 11 groups, based on characteristics. Newlands noticed that there were similarities between elements with atomic weights that differed by seven. He called this The Law of Octaves, drawing a comparison with the octaves of music. -
Julius Lothar Meyer
Julius Lothar Meyer, produced several Periodic Tables between 1864-1870.
1868 he incorporated the transition metals in a much more developed table. This 1868 table listed the elements in order of atomic weight, with elements with the same valency arranged in vertical lines. Meyer did contribute to the development of the periodic table in another way though. -
Dimitri Mendeleev
Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them. -
Antoine Bequerel
French physicist Antoine Bequerel first discovered radioactivity. Thomson student from New Zealand 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, and subsequently discovered radium and polonium. They discovered that beta particles were negatively charged. -
William Ramsay and Lord Rayleigh
Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0. -
J. J. Thomson
J. J. Thomson first discovered electrons; small negatively charged particles in an atom. John Townsend and Robert Millikan determined their exact charge and mass. -
Bequerel
Bequerel discovered that electrons and beta particles as identified by the curies are the same thing. -
Rutherford
Rutherford announced that radioactivity is caused by the breakdown of atoms. -
Element
Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom. -
Henry Moseley
The periodic table was arranged by atomic mass, and this nearly always gives the same order as the atomic number. However, there were some exceptions like iodine and tellurium, see above, which didn’t work. Mendeleev had seen that they needed to be swapped around, but it was Moseley that finally determined why. He fired the newly-developed X-ray gun at samples of the elements, and measured the wavelength of X-rays given. He used this to calculate the frequency and found that when the square -
James Chadwick
James Chadwick first discovered neutrons, and isotopes were identified. This was the complete basis for the periodic table. In that same year Englishman Cockroft and the Irishman Walton first split an atom by bombarding lithium in a particle accelerator, changing it to two helium nucleius. -
Glenn Seaborg
Glenn Seaborg identified lanthanides and actinides, atomic number , which are usually placed below the periodic table.
