Tellurium trioxide is an inorganic chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 of tellurium and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. In this compound, tellurium is in the +6 oxidation state

Oxidation state

In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

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Polymorphs

There are two forms, yellow-red α-TeO₃ and grey, rhombohedral, β-TeO₃ which is less reactive.

α-TeO₃ has a structure similar to FeF₃

Iron(III) fluoride

Iron fluoride, also known as ferric fluoride, is an inorganic compound. It exists in an anhydrous form as well as two hydrated forms . It is produced commercially mostly for laboratory work and is not as useful as the related compound iron chloride...

 with octahedral TeO₆ units that share all vertices.

Preparation

α-TeO3 can be prepared by heating orthotelluric acid, Te(OH)₆ at over 300°C . The β-TeO₃ form can be prepared by heating α-TeO₃ in a sealed tube with O₂ and H₂SO₄.

α-TeO₃ is unreactive to water but is a powerful oxidising agent when heated. With alkalis it forms tellurates.

α-TeO₃ when heated loses oxygen to form firstly Te₂O₅ and then TeO₂

Tellurium dioxide

Tellurium dioxide is a solid oxide of tellurium. It is encountered in two different forms, the yellow orthorhombic mineral tellurite, β-TeO2, and the synthetic, colourless tetragonal , α-TeO2...

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