Element Chromium, Cr, Transition Metal. Chromium is closely related to manganese in the number of the series of compounds which it forms. Whereas, however, in the case of manganese, the acids corresponding to the higher stages of oxidation were somewhat unstable, these belong in the case of chromium to the most important and best-known compounds. Salts of the divalent dichromion, Cr. Salts of the trivalent trichromion, Cr.

Element Manganese, Mn, Transition Metal. The element manganese is very closely related to iron. It differs from it in being more readily oxidised, and in its higher compounds being more readily formed than in the case of iron. For the rest, the corresponding compounds of manganese and iron are very similar to one another, and in many cases are isomorphous. In nature, manganese occurs very widely distributed, but is much less abundant than iron. It is found chiefly as manganese peroxide, Mn.

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 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 Tungsten, W, Transition Metal. Was produced by de Elhuyar brothers, students of Bergman in 1783. They named the new metal wolfram. After the mineral wolframite in which tungsten. Miners of 1416 centuries noticed that roasting of the ore tales the tin away, transferring it into slag.

Element Rhenium, Re, Transition Metal. Is the rarest and much dispersed trace element. Its average abundance is 7x10. Is the rarest element with stale isotopes.