Element Niobium, Nb, Transition Metal. Main article History of Niobium. After Niobe, daughter of Tantalus in Greek mythology. Main article Occurrence of Niobium. The crustal abundance of Niobium. It occurs in the minerals columbite columbite-tantalite or coltan, pyrochlore and loparite.

Element Samarium, Sm, Lanthanide. Samarium is one of the less common of the rare earth elements, being on the one hand much less abundant than the other elements of the cerium group, and on the other hand much more abundant than europium, terbium, and thulium. It is about as plentiful as gadolinium. Samarium is a yellow metal of density 7. The metal quickly tarnishes in the air. Extracted by Mosander from ceria earth. The samarskite mineral was named.

Element Tantalum, Ta, Transition Metal. The discovery of transition metal tantalum. Symbolizing oxide is insoluble in acid, and was unable, just as the mythological Tantalos. Ekeberg called the ores in which tantalum. Was discovered tantalite and yttrotantalite. Perhaps Ekeberg isolated impure tantalum. Deep layers and upper mantle are poor by tantalum.

Element Titanium, Ti, Transition Metal. Titanium occurs in the crust of the earth in the form of its dioxide, Ti. Which, like silica, is either in the free state or combined with metallic oxides, forming titanates. Impure titanium dioxide is found in three distinct crystalline forms as rutile, brookite, and anatase; ilmenite or titanic iron ore is Fe. Titanite or sphene, Ca. Igneous rocks contain an average of 0. 74 per cent, of Ti.

Element Hafnium, Hf, Transition Metal. In 1911 Urbain noticed several new lines in spectrum of the fractions of yttria mother solution and, thinking he had found a new element similar to the rare earths, called it celtium.

Element Lanthanum, La, Lanthanide. Lanthanum is a tin-white metal of density 6. It is malleable, but not ductile. Measurements made with material of doubtful purity indicate that lanthanum is feebly paramagnetic, but this is questionable. 923 and its heat of formation 97. it resembles the corresponding cerium compound.

Element Yttrium, Y, Transition Metal. As an element of the 3. Group in periodic system, does not belong to the group rare earth metals; however the history of its discovery is closely connected with rare earth elements. A lustrous black color mineral. Ekeberg extracted an earth from this mineral and named it yttria. 45 years later Mosander extracted yttrium.