PTL:Tellurium
From ChemEd Collaborative
Tellurium is a metalloid in Group VIA (Group 16) and the 5th period. Other elements in the group are oxygen (O), sulfur (S), selenium (Se), and polonium (Po).
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Discovered
Tellurium was discovered 1782, before selenium and polonium were known. The discovery was made by an Austrian, Müller von Rechenstein, but the element was named by Klaproth, the discoverer of zirconium and uranium.
Name
The name, and symbol, come from the Latin word for "earth" (tellus).
Characteristics
The element is more metallic than O, S, and Se, but it resembles them chemically. Oxygen and sulfur are electrical insulators, Se and Te are semiconductors, and polonium is clearly a metal. Te has oxidation numbers of -2, 0, +2, +4, and +6.
Unlike S and Se, which exhibit a number of allotropic forms, Te has only one crystalline form, a network of spiral chains of Te atoms.
Found
Most tellurium is recovered in the process of electrolytically refining copper. It is found in nature as the free element but also as gold telluride, AuTe2.
Reactions
The element is not attacked by aqueous HCl, but it is oxidized by nitric acid. It burns in air with a green-blue flame to give TeO2. It dissolves in aqueous NaOH in the presence of air to give deep red solutions.
Uses
Tellurium and its compounds have found use in pigments, catalysts in [petroleum] cracking, lubricants, semiconductors, rubber, and steel additives.
Compounds of Te are probably toxic and should be handled with care. Exposure to traces of Te compounds in the air will lead to "tellurium breath", a garlic-like odor.
Emission Spectra
This is the emission spectra for Tellurium.
