chemistry

Tellurium compounds

Tellurium compounds is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tellurium compounds rather than just read about it. In short: Tellurium compounds are compounds containing the element tellurium (Te). Tellurium belongs to the chalcogen (group 16) family of elements on the periodic table, which also includes oxygen, sulfur, selenium and polonium: Tellurium and selenium compounds are similar.

Key takeaways

Tellurium compounds belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tellurium compounds to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tellurium compounds from memory before moving on to harder problems.

Reference excerpt

Tellurium compounds are compounds containing the element tellurium (Te). Tellurium belongs to the chalcogen (group 16) family of elements on the periodic table, which also includes oxygen, sulfur, selenium and polonium: Tellurium and selenium compounds are similar. Tellurium exhibits the oxidation states −2, +2, +4 and +6, with +4 being most common.

Tellurides

Reduction of Te metal produces the tellurides and polytellurides, Ten2−. The −2 oxidation state is exhibited in binary compounds with many metals, such as zinc telluride, ZnTe, produced by heating tellurium with zinc. Decomposition of ZnTe with hydrochloric acid yields hydrogen telluride (H2Te), a highly unstable analogue of the other chalcogen hydrides, H2O, H2S and H2Se:

H2Te is unstable, whereas salts of its conjugate base [TeH]− are stable.

Halides

The +2 oxidation state is exhibited by the dihalides, TeCl2, TeBr2 and TeI2. The dihalides have not been obtained in pure form, although they are known decomposition products of the tetrahalides in organic solvents, and the derived tetrahalotellurates are well-characterized:

where X is Cl, Br, or I. These anions are square planar in geometry. Polynuclear anionic species also exist, such as the dark brown Te2I2−6, and the black Te4I2−14. With fluorine Te forms the mixed-valence Te2F4 and TeF6. In the +6 oxidation state, the –OTeF5 structural group occurs in a number of compounds such as HOTeF5, B(OTeF5)3, Xe(OTeF5)2, Te(OTeF5)4 and Te(OTeF5)6. The square antiprismatic anion TeF2−8 is also attested. The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (TeCl4, TeBr4 and TeI4) in the +4 state, and other lower halides (Te3Cl2, Te2Cl2, Te2Br2, Te2I and two forms of TeI). In the +4 oxidation state, halotellurate anions are known, such as TeCl2−6 and Te2Cl2−10. Halotellurium cations are also attested, including TeI+3, found in TeI3AsF6.

Oxocompounds

Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of TeSO3 in vacuum, disproportionating into tellurium dioxide, TeO2 and elemental tellurium upon heating. Since then, however, existence in the solid phase is doubted and in dispute, although it is known as a vapor fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide. Tellurium dioxide is formed by heating tellurium in air, where it burns with a blue flame. Tellurium trioxide, β-TeO3, is obtained by thermal decomposition of Te(OH)6. The other two forms of trioxide reported in the literature, the α- and γ- forms, were found not to be true oxides of tellurium in the +6 oxidation state, but a mixture of Te4+, OH− and O−2. Tellurium also exhibits mixed-valence oxides, Te2O5 and Te4O9. The tellurium oxides and hydrated oxides form a series of acids, including tellurous acid (H2TeO3), orthotelluric acid (Te(OH)6) and metatelluric acid ((H2TeO4)n). The two forms of telluric acid form tellurate salts containing the TeO2–4 and TeO6−6 anions, respectively. Tellurous acid forms tellurite salts containing the anion TeO2−3.

Other chalcogenides A disulfide, TeS2, forms when tellurous acid (H2TeO3) is mixed with hydrogen sulfide, but is unstable above −20 °C. In contrast, many thiotellurate anions are known, including TeS2−3, Te(S5)x(S7)2-y (x + y = 2). Many of these arise from the action of tellurium metal on polysulfide anions, although a solid-state synthesis is also possible. Despite their similarities to sulfo-selenide anions, the thiotellurates are not catenation products; instead, the sulfur ligands coordinate to the tellurium as heavier congeners to a tellurate. A thiosubtellurite, TeS2−2, is also known. These compounds are of interest because of their potential for ionic conductivity. Analogous selenotellurates are also known.

Zintl cations When tellurium is treated with concentrated sulfuric acid, the result is a red solution of the Zintl ion, Te2+4.

The oxidation of tellurium by AsF5 in liquid SO2 produces the same square planar cation, in addition to the trigonal prismatic, yellow-orange Te4+6:

Other tellurium Zintl cations include the polymeric Te2+7 and the blue-black Te2+8, consisting of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with tungsten hexachloride:

Interchalcogen cations also exist, such as Te2Se2+6 (distorted cubic geometry) and Te2Se2+8. These are formed by oxidizing mixtures of tellurium and selenium with AsF5 or SbF5.

Organotellurium compounds

Tellurium does not readily form analogues of alcohols and thiols, with the functional group –TeH, that are called tellurols. The –TeH functional group is also attributed using the prefix tellanyl-. Like H2Te, these species are unstable with respect to loss of hydrogen. Telluraethers (R–Te–R) are more stable, as are telluroxides.

Tritelluride quantum materials Recently, physicists and materials scientists have been discovering unusual quantum properties associated with layered compounds composed of tellurium that's combined with certain rare-earth elements, as well as yttrium (Y). These novel materials have the general formula of R Te3, where "R " represents a rare-earth lanthanide (or Y), with the full family consisting of R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er & Tm (not yet observed are compounds containing Pm, Eu, Yb & Lu). These materials have a two-dimensional character within an orthorhombic crystal structure, with slabs of R Te separated by sheets of pure Te. It is thought that this 2-D layered structure is what leads to a number of interesting quantum features, such as charge-density waves, high carrier mobility, superconductivity under specific conditions, and other peculiar properties whose natures are only now emerging. For example, in 2022, a small group of physicists at Boston College in Massachusetts led an international team that used optical methods to demonstrate a novel axial mode of a Higgs-like particle in R Te3 compounds that incorporate either of two rare-earth elements (R = La, Gd). This long-hypothesized, axial, Higgs-like particle also shows magnetic properties and may serve as a candidate for dark matter.

See also Sulfur compounds Selenium compounds Polonium compounds

References

Illustrations

Worked examples

Example 1 — a first encounter with Tellurium compounds

Start with the simplest possible case. Write down what Tellurium compounds claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tellurium compounds before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tellurium compounds ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tellurium compounds

In research: Tellurium compounds appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tellurium compounds in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tellurium compounds is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical compounds by element, Tellurium compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Tellurium compounds outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tellurium compounds in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tellurium compounds means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tellurium compounds out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tellurium compounds in simple terms?

Why does Tellurium compounds matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tellurium compounds?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tellurium compounds.