Mendeleev and the Prediction of Gallium

Mendeleev left a gap labeled eka-aluminum in his 1869 table and predicted its atomic weight, density, and oxide formula. In 1875 Paul-Emile Lecoq de Boisbaudran discovered gallium, matching nearly every forecast. The vindication silenced skeptics of the periodic law. Gallium melts in your palm at 29.8 degrees C and powers LEDs today..

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