Tellurium

In the early 1780s, Austrian chemist Franz-Joseph Müller von Reichenstein began investigating a gold ore that’d been found in a Romanian mine. The ore contained a strange substance that Müller thought must be bismuth sulfide. This turned out not to be correct, and Müller then declared that the substance was an unknown metal that was a lot like antimony.

After three years of research, Müller discovered that the new metal didn’t resemble antimony so much after all. For this reason, Müller took to referring to the substance as aurum paradoxium (paradoxical gold) and metallum problematicum (problem metal). Even the best chemists get frustrated now and then!

Müller published a paper in a journal, announcing the discovery of a new element. But because the journal wasn’t well known, the announcement didn’t get much attention. In 1796, Müller sent some of the gold ore to famed German chemist Martin Klaproth. Klaproth confirmed that the metal (which would turn out to be a metalloid rather than a true metal) was a new element. Klaproth chose the name tellurium for the element, from the Latin word tellus, meaning Earth.

This name was in keeping with the supposed correspondence of certain metals with the planets. For example, the Moon was associated with silver, Mars with iron, Saturn with lead, Mercury with mercury, and so on. When Klaproth discovered uranium in 1789, he named the element after Uranus. So the name “tellurium,” which connected the new element with the Earth, made sense!

Tellurium is a semi-metal that’s commonly processed into a grey powder. The element has two allotropes, or forms. One of these allotropes is crystalline, silvery, brittle, and easily crushed. The other allotrope is an amorphous black-brown powder. Tellurium is a chalcogen, meaning it shares qualities with oxygen, sulfur, selenium, polonium, and livermorium.

Today, most tellurium is used in cadmium telluride photovoltaic cells. Tellurium is helping make the transition to renewable energy possible!

Previously, most tellurium was used in steel alloys. By adding tellurium to steel, steel becomes a lot easier to machine. Tellurium has also been used to catalyze reactions in oil processing, in vulcanizing rubber, and in the ceramics that make certain electronic devices function.

Tellurium suboxide has been used in some types of CDs and DVDs. When tellurium bonds with halogens like chlorine, tellurium can take on the electron configuration of xenon. 

Gold and silver are often found compounded with tellurium. Cadmium telluride, a compound of cadmium and tellurium, is used in photovoltaic cells. Other tellurium compounds have been used as brown or blue ceramic pigments. Diphenyl ditelluride can be used to remove oxygen from, or reduce, certain organic compounds. 

In nature, tellurium is found in eight isotopes. Six of these—tellurium-120, tellurium-122, tellurium-123, tellurium-124, tellurium-125, and tellurium-126—are stable (non-radioactive). Tellurium-128 and tellurium-130 are unstable (radioactive), but they both have very long half-lives. In fact, tellurium-128 has the longest known half-life of any radioactive element: its half-life is 160 trillion times the age of the known universe!

Researchers have created 31 other tellurium isotopes. All these isotopes have half-lives of 19 days or less.

Most tellurium is extracted from the byproducts of copper ore processing. Tellurium prices have gone up in recent years as demand has increased, especially as the metal has been used in solar cells. The United States, Canada, and Peru are the top tellurium producers.