Background on the Periodic Table
A Russian scientist named Dimitri Mendeleev developed the first Periodic Table of the Elements in 1869. In his table, he grouped the elements by mass and property trends. He predicted the existence of missing elements and their properties by showing where there were breaks in the table. Mendeleev's creation, though, did not answer the question of the causes of certain mass oddities nor did it explain chemical activities.
Later, Brit Henry Moseley organized the table by atomic number. He developed the periodic law, stating that properties of elements are a periodic function of the atomic numbers. Properties include reactivity, melting points, and atomic radius.
|Dimitri's Original Periodic Table of the Elements|
|8||Cs=133||Ba=137||?Di=138||?Ce=140||?||?||?||? ? ? ?|
|12||?||?||?||Th=231||?||U=240||?||? ? ? ?|
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