- Tellurium (Te) is a metalloid with atomic number 52, positioned in Group 16 of the periodic table alongside oxygen, sulfur, selenium, and polonium.
- It has a silvery-white, brittle, crystalline appearance with a metallic luster.
- Tellurium’s chemical behavior is intermediate between metals and nonmetals, though it tends to form covalent compounds and exhibits multiple oxidation states, most commonly –2, +4, and +6. It has six valence electrons—two in the 5s subshell and four in the 5p subshell. Its atomic structure consists of fifty-two protons, typically seventy-six neutrons, and fifty-two electrons arranged in five shells.
- Naturally occurring tellurium consists of eight stable isotopes, with tellurium-130 (¹³⁰Te) being the most abundant at about 34.08%. Interestingly, some isotopes such as tellurium-128 (¹²⁸Te) and tellurium-130 are very weakly radioactive, undergoing double beta decay with half-lives far exceeding the age of the universe.
- Tellurium is a relatively rare element in the Earth’s crust, with an average abundance of only about 0.001 parts per million, making it less common than gold or platinum. It is typically found in combination with gold, silver, copper, and lead, most notably in minerals such as tellurite (TeO₂), calaverite (AuTe₂), and sylvanite ((Au,Ag)Te₂). The element is primarily obtained as a byproduct of copper refining, particularly from the anode slimes produced during electrolytic copper extraction. Major producers include the United States, Canada, Peru, Japan, and Russia.
- Tellurium was discovered in 1782 by Austrian mineralogist Franz-Joseph Müller von Reichenstein while analyzing a gold-bearing ore from Transylvania. Initially, Müller suspected the ore contained bismuth, but after further investigation, he recognized it as a new element. The name “tellurium” was later given by German chemist Martin Heinrich Klaproth in 1798, derived from the Latin tellus, meaning “earth.”
- In modern applications, tellurium is most significant in metallurgy and electronics. It is used to improve the machinability of copper and stainless steel, to strengthen and harden lead in batteries, and to produce thermoelectric devices capable of converting heat into electricity. Tellurium compounds such as cadmium telluride (CdTe) are important in thin-film solar cells, offering high efficiency and low manufacturing costs. Bismuth telluride (Bi₂Te₃) is a key material for thermoelectric cooling modules.
- Chemically, tellurium resembles selenium and sulfur, forming compounds such as hydrogen telluride (H₂Te), tellurium dioxide (TeO₂), and metal tellurides. It reacts with halogens and oxidizes upon heating in air to form tellurium dioxide, which is a useful intermediate in metallurgy and glass manufacturing. Tellurium imparts a deep wine-red color to glass and ceramics.
- Biologically, tellurium has no known essential role in humans and is generally toxic in large amounts. Even small exposures can cause “tellurium breath,” a distinctive garlic-like odor due to the formation of volatile tellurium compounds in the body. While rare, some microorganisms can metabolize tellurium compounds, reducing them to elemental tellurium.
- From an environmental perspective, tellurium is considered a critical raw material due to its rarity and essential role in green technologies such as solar cells and thermoelectrics. Recycling from industrial waste, electronic scrap, and photovoltaic panels is becoming increasingly important to meet growing demand and reduce reliance on primary mining.
