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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.
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Robert Boyle also discovered phosphorus, and it became public.
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The development of the periodic table begins with German chemist Johann Dobereiner (1780-1849) who grouped elements based on similarities.
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In 1809 at least 47 elements were discovered, and scientists began to see patterns in the characteristics.
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Dobereiner proposed the Law of Triads: Middle element in the triad had atomic weight that was the average of the other two members.
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In 1863 English chemist John Newlands divided the than discovered 56 elements into 11 groups, based on characteristics.
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he wrote a paper proposing the Law of Octaves which was elements exhibit similar behavior to the eighth element following it in the table.
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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.
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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.
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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.
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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. -
In 1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0.
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J. J. Thomson first discovered electrons. John Townsend and Robert Millikan determined their exact charge and mass.
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Bequerel discovered that electrons and beta particles which were identified by the Curies are the same thing.
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Rutherford announced that radioactivity is caused by the breakdown of atoms.
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In 1906, Mendeleev came within one vote of receiving the Nobel Prize in chemistry.
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Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom.
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Bohr discovered that electrons move around a nucleus in energy called orbitals. Radiation is emitted during movement from one orbital to another.
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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.
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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.
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Glenn Seaborg identified lanthanides and actinides, which are usually placed below the periodic table.
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By 1860 about 60 elements were known.
