Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth. Tellurium-bearing compounds were first discovered in 1782 in a gold mine in Kleinschlatten, Transylvania (now Zlatna, Romania) by Austrian mineralogist Franz-Joseph Müller von Reichenstein, although it was Martin Heinrich Klaproth who named the new element in 1798 after the Latin tellus 'earth'. Gold telluride minerals are the most notable natural gold compounds. However, they are not a commercially significant source of tellurium itself, which is normally extracted as a by-product of copper and lead production.

Commercially, the primary use of tellurium is CdTe solar panels and thermoelectric devices. A more traditional application in copper (tellurium copper) and steel alloys, where tellurium improves machinability, also consumes a considerable portion of tellurium production. Tellurium is considered a technology-critical element. Tellurium has no biological function, although fungi can use it in place of sulfur and selenium in amino acids such as tellurocysteine and telluromethionine. In humans, tellurium is partly metabolized into dimethyl telluride, (CH3)2Te, a gas with a garlic-like odor exhaled in the breath of victims of tellurium exposure or poisoning.

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Atomic properties

Standard atomic weight127.6 ±0.03
Atomic mass127.603 u

Atomic radii

Radius (empirical)140 pm
Radius (calculated)123 pm
Covalent radius138 ±4 pm
Van der Waals radius206 pm

Atomic shell

Electron configurationKr 4d10 5s2 5p4
Ionization energy(1st) 9.009808 eV
(2nd) 18.6 eV
(3rd) 27.84 eV
(4th) 37.4155 eV
(5th) 59.3 eV
(6th) 69.1 eV
Shell model

Physical properties

Density6.24 g·cm−3
Molar volume2.046·10-5 m3·mol−1
Speed of sound2,610 m·s−1 (293.1 K)


Melting point722.6 K
Boiling point1,261 K
Liquid range538.3 K
Transition temperature7.4 K


Melting enthalpy17.5 kJ·mol-1
Enthalpy of vaporization48 kJ·mol-1
Binding energy197 kJ·mol-1

Heat and conductivity

Thermal conductivity3 W·m-1·K-1


Mohs hardness2.25
Brinell hardness180 NM·m-2

Elastic properties

Young’s modulus43 GPa
Shear modulus16 GPa
Bulk modulus65 GPa

Electrical properties

Electrical conductivity10,000 S·m-1
Resistance0.001 Ωm


Magnetic susceptibility-3.95·10-5 cm3·mol−1 (298 K)

Optical properties

Reflectivity50 %
Refractive index1

Chemical properties

Basicityslightly acidic
Oxidation state-2, (±1), 2, 4, 6
Standard potential-1.143 V (Te + 2e- → Te2-)


Pauling scale2.1
Sanderson scale2.62
Allred-Rochow scale2.01
Mulliken scale2.41
Allen scale2.158
Ghosh-Gupta scale5.325 eV
Nagle scale2.08
Pearson absolute negativity5.49 eV

Other properties

Natural occurrenceprimordial
Crystal structureHexagonal
Goldschmidt Classificationchalcophile
Superconductorwith transition tempperature under special conditions
Price/kg63.5 USD

Natural abundances

9 ppb ≈ 9.04·1010 M☉
2,100 ppb ≈ 2.09 g
Earth’s crust
1 ppb ≈ 27.7 Mt