What is the most common oxidation state of tellurium?

Tellurium has two common oxidation states: −2 (telluride, Te²⁻) in ionic and covalent compounds with metals, and +4 in oxides and halides. The −2 state dominates in binary compounds with electropositive metals (CdTe, Bi₂Te₃, H₂Te), while +4 is the most stable positive state in ordinary chemistry (TeO₂, TeCl₄, H₂TeO₃).

Why does tellurium have a −2 oxidation state?

Tellurium's electron configuration [Kr] 4d¹⁰ 5s² 5p⁴ means it has four valence p-electrons and needs two more to fill the 5p shell. Gaining two electrons gives the telluride ion Te²⁻ with a [Kr] 4d¹⁰ 5s² 5p⁶ noble-gas-like configuration. This mirrors sulfide (S²⁻) and selenide (Se²⁻) chemistry in Group 16.

What is the +6 oxidation state of tellurium?

The +6 state occurs when tellurium loses all six valence electrons (5s² 5p⁴). It is found in telluric acid H₂TeO₄ (or Te(OH)₆ in the octahedral form) and tellurate salts (TeO₄²⁻). Unlike sulfuric acid, orthotelluric acid Te(OH)₆ is octahedral and far less acidic, reflecting the larger size and more metallic character of Te.

How does the +4 state compare to +6 in stability?

The +4 state is more stable than +6 under ordinary conditions. This is partly attributable to the inert pair effect: the 5s² electron pair in Period 5 elements is harder to ionize than in lighter analogs, making full oxidation to +6 less energetically favorable than for sulfur. TeO₂ is stable, while TeO₃ and tellurates are oxidizing agents that revert to Te(IV) under mild reduction.

What are important industrial uses of tellurium compounds?

CdTe (cadmium telluride, oxidation state −2) is a leading thin-film photovoltaic material, converting sunlight to electricity at low manufacturing cost. Bi₂Te₃ (bismuth telluride) is the benchmark thermoelectric material for near-room-temperature applications. Tellurium is also alloyed into steel and copper for machinability improvement and used in phase-change memory materials (Ge₂Sb₂Te₅).

Is tellurium metal, nonmetal, or metalloid?

Tellurium is classified as a metalloid (or semimetal). It has a silvery crystalline appearance and semiconducting electrical properties but is brittle and not ductile like a true metal. Its chemistry is predominantly nonmetallic (forming anions and covalent compounds) while its physical properties sit at the boundary between metals and nonmetals — consistent with its position at the bottom of Group 16 before polonium.

Tellurium Oxidation States

Name: Tellurium Oxidation States
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Author: Nham Vu

Reference and explorer for all known oxidation states of tellurium (Te, Z=52), with electron configuration, stability notes, and key compounds.

Atomic # 52 Te Tellurium

Atomic Mass

127.60 u

Group

16 (VIA)

Period

Block

p-block

Electronegativity

2.1 (Pauling)

Oxidation States

−2, 0, +2, +4, +6

Tellurium exhibits five oxidation states: −2, 0, +2, +4, and +6. As a Group 16 chalcogen with configuration [Kr] 4d¹⁰ 5s² 5p⁴, tellurium can either gain two electrons (−2 telluride) or lose 2, 4, or all 6 valence electrons. The −2 state is the most common in binary compounds with metals; the +4 state is the most stable positive oxidation state; and the +6 state requires strongly oxidizing conditions, partly hindered by the inert pair effect of the 5s² electrons.

Oxidation State	Stability	Notes
−2	Common — most stable anion	Telluride ion Te²⁻; mirrors sulfide and selenide chemistry. Present in CdTe (solar cells), Bi₂Te₃ (thermoelectrics), Ag₂Te, and H₂Te (hydrogen telluride, a toxic gas). Gaining two electrons fills the 5p shell to a noble-gas-like [Kr]4d¹⁰5s²5p⁶ configuration.
0	Elemental only	Elemental tellurium; a silvery-white crystalline metalloid. Semiconducting; brittle. The stable allotrope has a helical chain structure in the solid state.
+2	Uncommon	Found in TeCl₂ and some organic tellurides (R₂Te). Less stable than +4; TeCl₂ disproportionates on heating. The lone pair on Te(II) makes it a ligand donor in some complexes.
+4	Most stable positive	The dominant positive oxidation state. Found in TeO₂ (tellurium dioxide), TeCl₄, TeF₄, H₂TeO₃ (tellurous acid), and Te(OH)₂ intermediates. Stability is partly due to the inert pair effect — the 5s² lone pair is retained rather than lost to reach +6.
+6	Oxidizing conditions required	All six valence electrons are lost. Found in telluric acid H₂TeO₄ (or orthotelluric acid Te(OH)₆) and tellurate anion TeO₄²⁻. Unlike H₂SO₄, orthotelluric acid is octahedral and much weaker. TeO₃ is a mild oxidizer. The inert pair effect makes +6 less accessible than for sulfur or selenium.

Inert Pair Effect
In Period 5, the 5s² electron pair becomes increasingly difficult to remove due to relativistic contraction and poor shielding by the filled 4d shell. This stabilizes the +4 state relative to +6 for tellurium — the opposite trend seen in the lighter Period 2 analog sulfur, where +6 (in H₂SO₄) is the more stable higher state. The effect is even more pronounced in polonium (Po), directly below Te.

Tellurium compounds span all five oxidation states. The most commercially significant are the −2 tellurides used in semiconductors and thermoelectrics, and the +4 oxides and halides used as chemical intermediates. The +6 tellurates are specialist oxidizing reagents.

Compound	Formula	Te State	Notes
Hydrogen Telluride	H₂Te	−2	Colorless toxic gas; weaker acid than H₂S. Prepared by reaction of tellurides with acid. Highly malodorous.
Cadmium Telluride	CdTe	−2	Bandgap 1.44 eV; the leading thin-film photovoltaic absorber layer. Manufactured at multi-GW scale by First Solar.
Bismuth Telluride	Bi₂Te₃	−2	Benchmark thermoelectric material for near-room-temperature applications (ZT ≈ 1). Used in Peltier coolers and waste-heat generators.
Silver Telluride	Ag₂Te	−2	Black solid; mixed ionic-electronic conductor; phase-change memory research material. Found in nature as hessite mineral.
Lead Telluride	PbTe	−2	Thermoelectric for mid-temperature range (500–800 K); ZT up to 2 with nanostructuring. Used in radioisotope thermoelectric generators.
Tellurium Dioxide	TeO₂	+4	White solid; amphoteric oxide; the primary industrial tellurium compound. Used in acousto-optic devices and as a glass modifier.
Tellurium Tetrachloride	TeCl₄	+4	Colorless solid; hydrolyzes in moist air to TeO₂. Used as a starting material for organotelllurium synthesis.
Tellurium Tetrafluoride	TeF₄	+4	White crystalline solid; Lewis acid. Precursor to higher tellurium fluorides.
Tellurous Acid	H₂TeO₃	+4	Weak diprotic acid in solution; the Te(IV) oxoacid. Less well-defined than H₂SO₃; exists as hydrated TeO₂.
Telluric Acid	Te(OH)₆	+6	Orthotelluric acid; octahedral; Ka1 ≈ 2×10⁻⁸, far weaker than H₂SO₄. Oxidizing agent used in selective organic oxidations.
Tellurate Ion	TeO₄²⁻	+6	Found in tellurate salts (e.g., Na₂TeO₄). Mild oxidizer; used in analytical chemistry periodate-tellurate titrations.
Tellurium Hexafluoride	TeF₆	+6	Colorless gas; the most stable Te(VI) fluoride. Hydrolyzes slowly. Used in CVD for telluride thin film deposition.

Ground State Configuration

Paired valence s-electrons — inert pair; retained in +4 state

4 valence p-electrons; needs 2 more for −2 (Te²⁻) noble-gas config

Notation

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁴

Noble gas: [Kr] 4d¹⁰ 5s² 5p⁴

Te²⁻ ion: [Kr] 4d¹⁰ 5s² 5p⁶ (like Xe)

Te⁴⁺ ion: [Kr] 4d¹⁰ 5s² (5s pair retained — inert pair)

Note: tellurium has 6 valence electrons (5s² 5p⁴), analogous to sulfur (3s² 3p⁴) and selenium (4s² 4p⁴).

Ionization / Electron-Gain Steps

[Kr] 4d¹⁰ 5s² 5p⁴

Neutral atom — 6 valence electrons; metalloid

Te²⁻

[Kr] 4d¹⁰ 5s² 5p⁶

Gains 2 electrons → telluride ion; Xe-like closed shell; EA₁ ≈ −190 kJ/mol, EA₂ endothermic but stabilized in lattice

Te²⁺

[Kr] 4d¹⁰ 5s² 5p²

Loses two 5p electrons → Te(II); uncommon, seen in TeCl₂

Te⁴⁺

[Kr] 4d¹⁰ 5s²

Loses four 5p electrons → Te(IV); retains 5s² inert pair; most stable positive state in TeO₂, TeCl₄

Te⁶⁺

[Kr] 4d¹⁰

Loses all 6 valence electrons → Te(VI); found in Te(OH)₆ and TeF₆; requires strong oxidizer

Group 16 comparison: S vs Se vs Te
All three chalcogens share the ns² np⁴ valence pattern and the same set of oxidation states. Going down the group, the ns² inert pair effect grows stronger: sulfur readily reaches +6 (H₂SO₄ is a powerful oxidizer), selenium is intermediate, and tellurium is most stable at +4 — orthotelluric acid Te(OH)₆ is far weaker and less oxidizing than H₂SO₄. The −2 state remains important across all three, but Te²⁻ is a weaker base and softer anion than S²⁻ or Se²⁻, favoring bonds with heavier, softer metals like Cd, Bi, and Pb.

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Summary

Reference and explorer for all known oxidation states of tellurium (Te, Z=52), with electron configuration, stability notes, and key compounds.

How it works

Click a tab — Oxidation States, Compounds, Electron Config, or Physical Props — to explore each area.
The Oxidation States panel lists all five states (−2 through +6) with stability ratings and chemical context.
The Compounds panel covers key tellurium compounds grouped by oxidation state with formulas and applications.
The Electron Config panel shows orbital filling, ionization steps, and why certain states are preferred.
The Physical Props panel provides atomic and material data for quick reference.
Click any monospace table cell to copy its value to your clipboard.

Use cases

Students studying Group 16 trends and how tellurium compares to sulfur and selenium.
Chemistry teachers preparing lessons on chalcogen oxidation states and periodic trends.
Materials scientists working with CdTe photovoltaics or Bi₂Te₃ thermoelectric devices.
Researchers needing quick redox or atomic data for tellurium compounds.
Anyone preparing for chemistry exams covering Period 5 or Group 16 elements.

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Last updated: 2026-07-08 · Reviewed by Nham Vu