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1669 - Hennig Brand invented the Philosopher's Stone, which could turn metals into pure gold. He also discovered phosphorus
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1680 - Robert Boyle also discovered phosphorus without knowing about Hennig Brand's discovery.
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1863 - John Newlands organized the 56 then known elements into eleven separate groups based upon their atom structure.
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1869 - Dimitri Mendellev used John Newlands' grouping and organized the elements into what is now known as the periodic table.
He used the atomic mass as the primary characteristic to decide where each element belonged in his table. The elements were arranged in rows and columns. He even left spaces for elements to be discovered because of the pattern he saw once he started organizing those elements known at that that time. His table looked like this -
1886 - Antoine Becquerel discovered radioactivity.
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1894 - Sir William Ramsay and Lord Rayleigh discovered the noble gases and they were added to the periodic table as group O.
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1911 - Ernest Rutherford and Hans Geiger discovered that electrons moved around the nucleus of the cell's atom much like planets orbit the sun.
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1911 - Ernest Rutherford and Hans Geiger discovered that electrons moved around the nucleus of the cell's atom much like planets orbit the sun.
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1945 - Glenn Seaborg identified lanthanides and actinides which are elements with atomic numbers higher than 92 and are placed in a separate section on the bottom in today's Periodic Table.
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As of October 16, 2006 there are 117 different elements. The most recent elements discovered are meitnerium, darmstadtium, and ununquadium.
