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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. -
John Dalton's Law consisted of the idea that an atom is a universal entity which constructs everything.
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47 elements were discovered, and scientists began to see patterns in the characteristics.
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Johann Dobereiner discovered that elements with similar properties could be arranged by their atomic mass, yet always grouped in threes. Two elements being of higher value and lower value and one sitting exactly in the middle, coincidentally sharing the same characteristics. -
English chemist John Newlands divided the then discovered 56 elements into 11 groups, based on characteristics.
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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.
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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.
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Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0. -
English physicist J. J. Thomson first discovered electrons: small negatively charged particles in an atom. John Townsend and Robert Millikan determined their exact charge and mass.
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Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom. -
Bohr discovered that electrons move around a nucleus in discrete energy called orbitals. Radiation is emitted during movement from one orbital to another.
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English physicist Henry Moseley provided atomic numbers, based on the number of electrons in an atom, rather than based on atomic mass.
https://www.youtube.com/watch?v=D3GR6thtApI&t=66s -
James Chadwick first discovered neutrons, and isotopes were identified. This was the complete basis for the periodic table.
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Glenn Seaborg identified lanthanides and actinides (atomic number >92), which are usually placed below the periodic table. seaborg's discovery of the transuranium elements was the finalising piece to the puzzle for the periodic table , this final discovery gave the table the widely know shape that it holds today.
