A brief history of discovery: Scandium is the most advanced transition metal with an atomic number of only 21. However, in terms of discovery, Scandium is later than his neighbors on the periodic table of elements. Even in rare earth, Scandium is not found earlier. The reason for its late discovery is simple. The content of Scandium in the crust is only, which is equivalent to 5 grams per ton of crust material, much lower than other light elements. In addition, the separation of rare earth elements is very difficult, so it is not easy to find scandium from mixed minerals. However, although it has not been discovered, the existence of this element has been predicted. In the first edition of the periodic table of elements given by Mendeleev in 1869, a vacancy of atomic weight 45 was left behind calcium. Later, Mendeleev temporarily named the element after calcium as Eka-Boron, and gave some physical and chemical properties of this element.
Discovery process: In the late 19th century, the research on rare earth elements became a hot trend. One year before the discovery of scandium, de Marignac of Switzerland obtained a white oxide different from erbium earth by partially dissolving nitrate from the rose red erbium earth. He named this oxide ytterbium earth, which is the sixth place in the discovery of rare earth elements. L. F. Nilson (1840-1899) of Uppsala University in Sweden purified erbium earth according to Malinak's method and accurately measured the atomic weights of erbium and ytterbium (because at this time he was focusing on accurately measuring the physical and chemical constants of rare earth elements to verify the periodic law of elements).
After 13 times of partial decomposition, 3.5g pure ytterbium earth was obtained. But at this time, a strange thing happened. Malinak gave the atomic weight of ytterbium 172.5, while Nielsen got only 167.46. Nelson was keenly aware of what light elements might be inside. So he continued to process the obtained ytterbium earth with the same process. Finally, when only one tenth of the sample was left, the measured atomic weight dropped to 134.75; At the same time, some new absorption lines were also found in the spectra. Nelson named Scandium after his native Scandinavia. In 1879, he officially published his research results. In his paper, he also mentioned many chemical properties of scandium salt and scandium earth. However, in this paper, he did not give the exact atomic weight of scandium, nor did he determine the position of scandium in the element cycle.
Nelson's good friend, P.T. Cleve (1840~1905), who also teaches at Uppsala University, is also doing this work together. Starting from Erbium earth, he eliminated Erbium earth as a large number of components, and then separated out ytterbium earth and scandium earth, and found holmium and thulium, two new rare earth elements, from the residue. As a by-product, he purified scandium earth and further understood the physical and chemical properties of scandium. In this way, the drifting bottle released by Mendeleev was finally picked up by Cliff after sleeping for ten years.
