An Overview about the Chemical Element Niobium

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Symbol: Nb

Atomic Number: 41

Atomic Mass: 92.90638 amu

Melting Point: 2468.0 C (2741.15 K, 4474.4 F)

Boiling Point: 4927.0 C (5200.15 K, 8900.6 F)

Number of Protons: 41

Number of Electrons: 41

Number of Neutrons: 52

Classification: Transition Metal

Crystal Structure: Cubic

Density @ 293 K: 8.57 grams per cubic centimeter

Color: white

The discovery of the element Niobium was long, complicated and confusing. The story of its discovery starts in about 1734 when the first Governor of Connecticut found a new mineral which he called columbite. A sample of this new mineral was sent to London where it was stored in the mineral collection at the British Museum for many years.

In 1801 Charles Hatchett started an analysis on the columbite sample. From his work he concluded that the mineral contained an unknown element but he was unable to actually isolate the element. However he did name the element calling it columbium.

The next part of the story is where it starts to get confusing. In 1809 the English chemist and physicist William Hyde Wollaston decided to compare the two mineral ores columbite and tantalite. He concluded that columbium from the columbite was the same element as tantalum from tantalite. Both these elements are hard to isolate and are found together in both mineral ores.

The next scientist to play a part in this confusion was the German mineralogist and chemist Heinrich Rose who was working with samples of columbite and tantalite in 1844. He produced two new acids from these ores which he called niobic and pelopic acids. These he insisted were not the same as tantallic acid. Pelopic acid also contains niobium but at a lower oxidation state than niobic acid. He was not aware that he had just rediscovered columbium so he called his new element niobium from the Greek "Niobe" who in Greek mythology is the daughter of King Tantalus.

It was the Swiss chemist Jean Charles Galissard de Marignac who finally proved that tantalum and niobium were in fact different elements. Niobium metal was isolated in 1864 by the Swedish chemist Christian Wilhelm Blomstrand by heating niobium chloride in an atmosphere of hydrogen

For a long time the element had two names. In the United States it was called columbium while the rest of the world called it niobium. In 1950 the International Union for Pure and applied Chemistry gave the element the official name of niobium but Charles Hatchett is still credited with its discovery. While this name is now accepted by American chemical societies many American metallurgists and mineralogists still refer to the element as columbium.

The pure white metal is soft and ductile. When it is exposed to air for any length of time the metal will take on a bluish color. At temperatures in excess of 200 C (243 K, 392 F) niobium will oxidize in air. To prevent oxidization niobium processing can be carried out in a protective atmosphere such as nitrogen or one of the noble gases.

There is only one naturally occurring isotope of niobium. This is niobium-93 and it is stable. A number of unstable isotopes of niobium have been identified with mass numbers ranging from 81 to 113.

Today niobium is extracted from a number of ores but its primary ores are columbite (or niobite as it is now known) and pyrochlore.

One of the most recent uses for niobium is in the field of super-conductors. Alloys made with tin, aluminum and titanium are all super conductors. At temperatures below minus 263.9 C (9.25K, minus 442.75 F) pure niobium is a superconductor. The electron accelerator at the Thomas Jefferson National Accelerator Facility has 338 niobium super-conducting niobium cavities chilled with liquid helium. The electron accelerator is used to accelerate electrons to near the speed of light to study the quark structure of matter.

Other uses of niobium include jewelry and as arc welding rods. Niobium was used in the manufacture of air frames for the Gemini space program.

Discovery of the Elements by Mary Elvira Weeks Edition: 3 2003 ISBN 0766138720, 9780766138728

Los Alamos National Laboratory Chemical Division

More about this author: Alison Bowler

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