1754-Joseph Black isolated carbon dioxide, which he called "fixed air".
1778-Antoine Lavoisier wrote the first list of elements which contained 33 elements & distinguished between metals and non-metals
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1766-Henry Cavendish discovered hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air
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1773-1774Carl Wilhelm Scheele and Joseph Priestly independently isolated oxygen
1803-John Dalton proposed "Dalton's Law" describing the relationship between the components in a mixture of gases.
1828-Jakob Berzelius developed a table of atomic weights and introduced letters to symbolize elements
1828-Johann Dobereiner developed groups of 3 elements with similar properties
1864-John Newlands arranged the known elements in order of atomic weights
Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence electrons
1864-Dmitri Mendeleev produced a table based on atomic weights but arranged them with elements with similar properties under each other. His Periodic Table included the 66 known elements organized by atomic weights.
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1894-William Ramsay discovered the Noble Gases
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1900-Ernest Rutherford discovered that radioactivity was actually caused by decaying atoms
1913-Henry Moseley determined the atomic number of each of the elements
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Source: Periodic Table Timeline - History Timelines http://www.datesandevents.org/events-timelines/19-periodic-table-timeline.htm (accessed Oct 21, 2016).