Scandium
. Scandium, symbol Sc, soft, silver-white metallic element with an atomic number of 21. Scandium is one of the transition elements in the periodic table . Scandium was discovered in 1879 by the Swedish chemist Lars Fredrik Nilson, eight years after the Russian chemist Dmitry Ivanovich Mendeleyev had predicted, on the basis of the periodic law, that the element exists in nature and that its properties resemble those of the element boron . Scandium is sometimes regarded as one of the rare earth elements . Scandium occurs in rare minerals such as wolframite . It is 31st in order of abundance of the elements in the earth's crust. It forms trivalent, colorless salts. Scandium melts at about 1541° C (about 2806° F), boils at about 2836° C (about 5137° F), and has a specific gravity of 3.0. The atomic weight of scandium is 44.956.