How One Scientist Dreamt Up the Periodic Table
Dmitri Mendeleev was a Russian scientist who was driven to devise a system of classifying the chemical elements. In the 1860s, the 56 known elements were simply sorted by their atomic weight. This ignored other essential characteristics, which Mendeleev and other scientists noticed followed a periodic pattern-that is, roughly every seven elements share certain characteristics. But sorting the elements in this manner didn't work either, because the periodization got messy as the elements got heavier. Mendeleev soon became obsessed with devising a perfect table of elements. Finally, one February night (or so the story goes) Mendeleev retired after a long day of work. In his sleep, the chaos of ideas that flooded his waking mind sorted itself into a pattern -- the one we know today as the periodic table of elements.
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from Crash Course
Key Facts In This Video
Mendeleev was so sure of the predictions in his periodic table, that when a French scientist's discovery of one of these elements didn't match his data, Mendeleev said he was wrong—and he did end up being wrong. (2:40)
Today's periodic table is grouped into alkali metals, alkaline earth metals; transition metals; halogens; metals, metalloids, gases, and nonmetals; lanthanides; actinides; and noble gases. (5:05)
Other scientists were trying to discover the same thing, but a few things set Mendeleev apart: he was obsessive, and he realized that the periodicity of elements had far-reaching consequences. (7:22)