Chemical Properties
Niobium was discovered by Charles Hatchett in 1801 and isolated by Christian Blomstrand of Sweden in 1964. Its name was given after the Greek mythological ?gure Niobe, the daughter of Tantalos; tantalum always was associated with niobium. For many years, the terms “niobium” and “columbium”wereusedinterchangeably;however,thename “niobium” was of?cially adopted by International Union of Pure and Applied Chemistry (IUPAC) in 1950. Niobium is not a very rare element; its crustal abundance is 24ppm, which is similar or greater than those of many common elements, such as lead or cobalt.
Niobium is a shiny white, soft, and malleable metal. The element is inert to HCl, HNO3, or aqua regia at room temperature, slightly soluble in HF, but is attacked by alkali hydroxides or oxidizing agents at all temperatures. In pure
form, niobium is ductile, unless it is allowed to associate at elevated temperatures with common gases such as N2,H 2, or O2. Thus, when processed, it must be placed in a protective environment
No data were found in the literature; however, it might be assumed that niobium and most of their compounds are odorless. Niobium pentachloride (NbCl5) has pungent odor, because it decomposes slowly when heated, with Cl2 formation. Niobium in the form of dust is moderately explosive when exposed to ?ame or by chemical reaction.
Chemical Properties
shiny grey metallic solid
Physical properties
Niobium is a soft grayish-silvery metal that resembles fresh-cut steel. It is usually found inminerals with other related metals. It neither tarnishes nor oxidizes in air at room temperaturebecause of a thin coating of niobium oxide. It does readily oxidize at high temperatures(above 200°C), particularly with oxygen and halogens (group 17). When alloyed with tin andaluminum, niobium has the property of superconductivity at 9.25 Kelvin degrees.
Its melting point is 2,468°C, its boiling point is 4,742°C, and its density is 8.57 g/cm3.
Isotopes
There are 49 isotopes of niobium, ranging from Nb-81 to Nb-113. All are radioactiveand made artificially except niobium-93, which is stable and makes up all of theelement’s natural existence in the Earth’s crust.
Origin of Name
Niobium is named after the Greek mythological figure Niobe who was
the daughter of Tantalus. Tantalus was a Greek god whose name is the source of the
word “tantalize,” which implies torture: he cut up his son to make soup for other gods.
Occurrence
Niobium is the 33rd most abundant element in the Earth’s crust and is considered rare.It does not exist as a free elemental metal in nature. Rather, it is found primarily in severalmineral ores known as columbite (Fe, Mn, Mg, and Nb with Ta) and pyrochlore [(Ca,Na)2Nb2O6 (O, OH, F)]. These ores are found in Canada and Brazil. Niobium and tantalum[(Fe, Mn)(Ta, Nb)2O6] are also products from tin mines in Malaysia and Nigeria. Niobium is a chemical “cousin” of tantalum and was originally purified by its separation through theprocess known as fractional crystallization (separation is accomplished as a result of the differentrates at which some elements crystallize) or by being dissolved in special solvents. Todaymost of the niobium metal is obtained from columbite and pyrochlore through a complicatedrefining process that ends with the production of niobium metal by electrolysis of moltenniobium potassium fluoride (K2NbF7).
Characteristics
Some of niobium’s characteristics and properties resemble several other neighboring elementson the periodic table, making them, as well as niobium, difficult to identify. This isparticularly true for tantalum, which is located just below niobium on the periodic table.
Niobium is not attacked by cold acids but is very reactive with several hot acids such ashydrochloric, sulfuric, nitric, and phosphoric acids. It is ductile (can be drawn into wiresthrough a die) and malleable, which means it can be worked into different forms.
Hazard
Niobium is not considered reactive at normal room temperatures. However, it is toxic in itsphysical forms as dust, powder, shavings, and vapors, and it is carcinogenic if inhaled or ingested.
Carcinogenicity
No evidence was found that niobiumiscarcinogenic.Indeed,therearesomestudiessuggesting its antitumor activity. In the mouse study of Schroeder et al., occurrence of 23.6% of tumors in the niobiumtreated group (5–6.62ppm niobium in drinking water and diet for a lifetime) versus 34.8% for the controls was documented.
