On the periodic table, gallium was predicted by Dmitri Mendeleev and discovered in 1875.
Mendeleev left a gap in his 1869 periodic arrangement for an element he called “eka-aluminium.” He predicted several of its properties from the patterns of neighboring elements. French chemist Paul-Émile Lecoq de Boisbaudran discovered gallium in 1875 by spectroscopy and later isolated it, confirming much of Mendeleev’s forecast.
Gallium has atomic number 31 and symbol Ga. It is a soft, silvery metal with an unusually low melting point of about 29.8 °C, so it can melt in a warm hand while remaining solid at cooler room temperatures. Gallium’s discovery became one of the classic demonstrations that the periodic table could successfully predict unknown elements. Germanium was another major confirmation, but it was discovered in 1886, not 1875.