Chemistry

An Overview about the Chemical Element Tellurium



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Tellurium

Symbol: Te

Atomic Number: 52

Atomic Mass: 127.6 amu (atomic mass units)

Melting Point: 449.5 C (722.65 K, 841.1 F)

Boiling Point: 989.8 C (1262.95 K, 1813.64 F)

Number of Protons: 52

Number of Electrons: 52

Number of Neutrons: 76

Classification: Metalloid

Crystal Structure: Hexagonal

Density @ 293 K: 6.24 grams per cubic centimeter

Color: silver

The element tellurium was discovered in 1782 by Franz Joseph Muller von Reichenstein. This Romanian mining official was the inspector of mines, salt works and smelters in the Transylvanian region; he also had an interest in chemistry. Von Reichenstein extracted tellurium from a sample of the gold ore aurum album. At first he believed the metal he had extracted to be antimony but he soon realized that it was an entirely new element. The new element was not named until the German chemist Martin Heinrich Klaproth cited von Reichensteins' work in a paper in 1798. While naming the element tellurium Klaproth gave full credit for its discovery to von Reichenstein. The name tellurium is derived from the Latin word "tellus" which means earth.

Tellurium can be found free in nature but it is more commonly found in gold ores such as calaverite and krennerite or the silver ore sylvanite. Most tellurium is produced commercially as a by product from the production of copper. Pure tellurium has a metallic luster and is silvery white in color. The metal is quite brittle and can be pulverized easily.

There are eight naturally occurring isotopes of tellurium five of which are stable and the other three have extremely long half lives. The most abundant isotope at 34.08% is tellurium-130 which is unstable with a half life of about a sextillion years (that a one with twenty one zeros following it!). In addition to the naturally occurring isotopes there are nearly forty unstable isotopes of tellurium currently recognized.

Tellurium has a number of industrial uses.

* Its main use is as an alloying agent. A small amount of tellurium when added to steel and copper makes the metals easier to machine or mill. It is also added to lead to increase its resistance to sulfuric acid as well as adding to its strength.

* It is a semiconductor and as such is often doped with the metals silver, copper, tin or gold.

* Tellurium is a major ingredient in blasting caps.

* The element is used to color ceramics and glass.

* It was used in the casing of the first atom bomb.

* Potassium tellurite is added to the microbiological media used to isolate the causative organism of diphtheria.

A human inhaling as little as 0.01 milligram of tellurium in a cubic meter of air will develop a characteristic garlic smelling breath. It is best not to try this out as tellurium and all its compounds are toxic.

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