sep 14, 1869 - Dmitri Mendeleev - Classification of Elements (1869)
Description:
Mendeleev classified elements into 7 groups according to their atomic mass and found a correlation between atomic mass and the properties of an element. He arranged elements into a diagram called the Periodic Table. The table created by Mendeleev also alotted spaces for elements that hadn't been discovered yet and were found later in history.
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Atomic Theory Timeline
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