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Tellurium

physical science Maturity 7-9 Next article →

Tellurium is a rare and fascinating chemical element with the symbol Te and atomic number 52.

Tellurium element
Tellurium element

It is classified as a metalloid, meaning it possesses properties of both metals and non-metals. Specifically, it is a silver-white, brittle substance that is easily pulverized into powder. Tellurium belongs to a chemical family called the chalcogens, which includes oxygen, sulfur, and selenium. While it is quite abundant throughout the universe, it is extremely rare in the Earth's crust. Its abundance on our planet is comparable to that of platinum, at about 1 microgram per kilogram.

Tellurium-89043
Tellurium-89043

The scarcity of tellurium on Earth is likely due to the way our planet formed. During the hot nebular formation of Earth, tellurium formed a volatile hydride. This hydride is a gas that allowed the tellurium to escape into space. This process is similar to what happened to selenium, another heavy element. Scientists believe these elements were depleted during preaccretional sorting in the solar nebula. In the cosmos, however, tellurium is actually more common than the element rubidium. This highlights the difference between how much of an element exists in space versus how much remains on Earth.

Tellurium can exist in two different physical forms, known as allotropes. The crystalline form is silvery-white and has a metallic luster. These crystals are trigonal and chiral, meaning they have a specific spatial structure. The atoms in crystalline tellurium are arranged in parallel helical chains. There are three atoms per turn in these chains. The second form is amorphous tellurium, which is a black-brown powder. This powder is created by precipitating tellurium from a solution of tellurous acid or telluric acid.

TeO2powder
TeO2powder

The history of tellurium involves many years of scientific investigation. In 1782, Franz-Joseph Müller von Reichenstein discovered tellurium-bearing compounds in a gold mine in Transylvania. At first, he was confused by the metal's strange properties. He called it "aurum paradoxum" or "problem metal" because it did not behave like antimony. It was not until 1798 that Martin Heinrich Klaproth named the element. He derived the name from the Latin word "tellus," which means earth.

Martin Heinrich Klaproth
Martin Heinrich Klaproth

Klaproth successfully isolated the element from the mineral calaverite.

Most tellurium is not mined directly but is recovered as a by-product. It is often extracted during the production of copper and lead. For example, it is found in anode sludges during the electrolytic refining of blister copper. To extract it, the sludge is roasted at 500 degrees Celsius with sodium carbonate. This process converts the telluride into sodium tellurite. This substance can then be leached with water. Finally, the tellurium is produced from tellurium dioxide through electrolysis or by reacting it with sulfur dioxide.

Tellurium element
Tellurium element

Today, tellurium is essential for several high-tech industries. Its primary commercial use is in Cadmium Telluride (CdTe) solar panels.

NREL Array
NREL Array

These thin-film solar cells are vital for renewable energy. Tellurium is also used in thermoelectric devices, which convert heat into electricity. In the metal industry, it is added to copper and steel alloys. This addition improves "machinability," making the metals easier to shape with machines. In the early 1920s, Thomas Midgley Jr. found it could prevent engine knocking, but the difficult smell made it impractical for fuel.

Tellurium also has interesting connections to biology and space. While it has no biological function in humans, some fungi can use it in amino acids. In humans, exposure can lead to the production of dimethyl telluride, a gas that causes a garlic-like odor on the breath. On a much larger scale, tellurium is created in the universe during massive cosmic events. In 2023, astronomers detected tellurium being created during a neutron star merger.

NuSTAR detector
NuSTAR detector

This shows that even rare elements on Earth have origins in the most powerful explosions in space.

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🖼️ Images & Media (8)
File:Tellurium element.jpg
Tellurium element.jpg
File:Tellurium-89043.jpg
Tellurium-89043.jpg
File:Martin Heinrich Klaproth.jpg
Martin Heinrich Klaproth.jpg
File:TeO2powder.jpg
TeO2powder.jpg
File:Zintl ion.jpg
Zintl ion.jpg
File:NREL Array.jpg
NREL Array.jpg
File:NuSTAR detector.JPG
NuSTAR detector.JPG
File:Swift's instrument Burst Alert Telescope (BAT) the detector plane.jpg
Swift's instrument Burst Alert Telescope...
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