Samples Containing Niobium or Tantalum

Overview

Niobium is named from Niobe the daughter of Tantalus in Greek Mythology. It was named Columbium (Cb) at the time of its discovery in 1801. This name was used until IUPAC adopted the name "niobium" in 1950 after more than a century of controversy.

Niobium (Nb) and tantalum (Ta)Tantalum (Ta), much like Zr and Hf, have nearly identical atomic radii. The radii of the ions (Nb⁺⁵ and Hf⁺⁵) are also almost identical which explains in part the fact that the chemistry of these two elements is so similar.

Nb and Ta are always found together in natural mineral deposits and both are relatively quite rare, with abundance estimates in the earths crust ranging from 0.01 to 0.0001 % m/m. The most important ores are Tantalite (Mn, Fe)·(Ta, Nb)₂O₆ containing 38-86 % m/m Ta₂O₅ and Columbite (Mn, Fe)·(Nb, Ta)₂O₆ containing 40-78% m/m Nb₂O₅. These formulas are written in such a way as to accommodate the fact that niobium and tantalum replace each other freely in these minerals in addition to the fact that Fe and Mn substitute for each other as well. Tantalum has a better corrosion resistance than Nb and is used for plating chemical apparatus which is in turn used for handling highly corrosive acid liquors and for radiation shields and crucibles in high-temperature vacuum furnaces. Niobium has a small thermal neutron capture cross-section and good resistance to several liquid-metal coolants. It is therefore of major interest in nuclear technology. Niobium is also found in a variety of alloys used for a variety of applications ranging from jet engines to bone implants.

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