Tellurium, represented by the symbol Te and atomic number 52, is a chemical element found in the periodic table. This brittle, mildly toxic, rare metalloid is silvery-white in its pure form and is primarily known for its unique crystalline structure that exhibits a silvery luster.
Discovered in 1782 by the Austrian chemist Franz-Joseph Müller von Reichenstein, tellurium was first identified as an impurity in gold ores. The element was later named by the German chemist Martin Heinrich Klaproth in 1798, deriving the name from the Latin word "tellus," meaning earth, to reflect its terrestrial origins and soil-like properties.
Chemical and Physical Properties
Tellurium is a member of the oxygen family, Group 16 on the periodic table, placing it in the same column as oxygen, sulfur, selenium, and polonium. It shares the typical characteristics of nonmetals yet possesses a metallic appearance, categorizing it as a metalloid. Its standard atomic weight is approximately 127.60 u, and it has a relatively high melting point of 449.51°C and a boiling point of 988°C.
- Appearance: Silvery-white lustrous solid
- Category: Metalloid
- Density: 6.24 g/cm³
- Electrical Conductivity: Semiconductor
Applications in Modern Industry
While relatively rare in the Earth's crust, tellurium plays a critical role in several high-tech industries. Its primary use is in the production of cadmium telluride (CdTe) photovoltaic cells, which are a significant component in thin-film solar panels due to their high efficiency and low-light performance.
In metallurgy, tellurium is utilized as an additive to copper and stainless steel to improve machinability. Alloys containing tellurium are easier to cut and shape, making them valuable in the manufacturing of precision instruments and machine parts. Furthermore, tellurium is a key ingredient in some types of blasting caps and other initiating devices.
Biological Role and Safety Considerations
Tellurium is not considered an essential nutrient for any known biological organism. In fact, it is generally regarded as toxic to humans and animals. Exposure to tellurium, even in relatively small amounts, can lead to a condition known as tellurium intoxication, which is characterized by a distinctive garlic-like odor on the breath and skin, metallic taste, and nausea.
Despite its toxicity, trace amounts of tellurium are found in the human body, likely originating from dietary sources such as grains and vegetables. Occupational safety regulations strictly limit exposure in industrial settings, requiring proper ventilation and protective equipment to mitigate the risks associated with handling the element.
Cosmic Origins and Rarity
The rarity of tellurium on Earth is partly explained by its cosmic origin. Studies of the element's isotopic composition suggest that tellurium is a product of the decay of unstable ruthenium isotopes found in meteorites. This indicates that the material forming the Earth and other terrestrial planets contained tellurium, but the element was largely lost to the atmosphere during the planet's formation due to its volatility.
Consequently, tellurium is much more abundant in the universe at large than it is within the Earth's crust. It is estimated to be one of the raindisc elements, making up only about 1 part per billion of the Earth's crust, which makes mining and commercial extraction a carefully calculated economic endeavor.
