Name: Tellurium
Symbol: Te
Atomic Number: 52
Atomic Weight: 127.600000
Family: Metalloids
CAS RN: 13494-80-9
Description: A silvery-white brittle solid.
State (25C): Solid
Oxidation states: +4, +6, -2

Molar Volume: 20.42 cm3/mole
Valence Electrons: 5p4

Boiling Point:  1261K, 988C, 1810F
Melting Point:
722.8K, 449.65C, 841.37F
Electrons Energy Level: 2, 8, 18, 18, 6
Isotopes: 32 + 5 Stable
Heat of Vaporization: 52.55 kJ/mol
Heat of Fusion: 17.49 kJ/mol
Density: 6.24 g/cm3 @ 300K
Specific Heat: 0.2 J/gK
Atomic Radius: 1.42
Ionic Radius: 0.97
Electronegativity: 2.1 (Pauling); 2.01 (Allrod Rochow)
Vapor Pressure: 23.1 Pa @ 449.65C
Tellurium (Latin, tellus meaning "earth") was discovered in 1782 by the Hungarian Franz-Joseph Muller von Reichenstein (Mller Ferenc) in Nagyszeben (now, Sibiu) Transylvania.  In 1789, another Hungarian scientist, Pl Kitaibel, also discovered the element independently, but later he gave the credit to Mller. In 1798, it was named by Martin Heinrich Klaproth who earlier isolated it.

Tellurium was used as a chemical bonder in the making of the outer shell of the first atom bomb.  The 1960s brought growth in thermoelectric applications for Tellurium, as well as its use in free-machining steel, which became the dominant use.

Tellurium is a relatively rare  brittle metalloid which looks like Tin and is chemically related to Selenium and Sulfur.

Tellurium can be alloyed with some metals to increase their machinability and is a basic ingredient in the manufacture of blasting caps.

Elemental Tellurium is occasionally found in nature but is more often recovered from various Gold ores, all containing AuTe2.  Tellurium is primarily used in alloys and as a semiconductor.


1s2 2s2p6 3s2p6d10 4s2p6d10 5s2p4


Tellurium is a relatively rare element, in the same chemical family as Oxygen, Sulfur, Selenium, and Polonium (the Chalcogens).

Silvery white metal-looking non-metal that is usually obtained as a dark grey powder.  It is unaffected by water and HCl, but burns in air or oxygen and dissolves in HNO3.

When crystalline, Tellurium is silvery-white and when it is in its pure state it has a metallic luster.  This is a brittle and easily pulverized metalloid.  Amorphous Tellurium is found by precipitating it from a solution of Tellurous or Telluric Acid (Te(OH)6). However, there is some debate whether this form is really amorphous or made of minute crystals.

Tellurium is a p-type semiconductor that shows a greater conductivity in certain directions which depends on atomic alignment.  Chemically related to Selenium and Sulfur, the conductivity of this element increases slightly when exposed to light.

It can be doped with Copper, Gold, Silver, Tin, or other metals. When in its molten state, Tellurium is corrosive to Copper, Iron, and stainless steel.

Tellurium gives a greenish-blue flame when burned in normal air and forms Tellurium Dioxide as a result.


Tellurium is found free in nature (native elemental form), but is most often found in the Telluride ores of Gold: Sylvanite (AgAuTe4), Calaverite (AuTe2) and Krennerite (AuTe2).  Tellurium compounds are the only chemical compounds of Gold found in nature, but Tellurium itself (unlike Gold) is also found combined with other elements (in metallic salts). The principal source of Tellurium is from anode sludges produced during the electrolytic refining of blister Copper.  It is a component of dusts from blast furnace refining of Lead.  Tellurium is produced mainly in the United States, Canada, Peru, and Japan.

2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10
5s2 5p4

Commercial-grade Tellurium is usually marketed as minus 200-mesh powder but is also available as slabs, ingots, sticks, or lumps. The year-end price for Tellurium in 2000 was $14 per pound.


Metal Alloys

Semiconductor Industry Uses:

Other Uses:

High purity metalorganics of both Selenium and Tellurium are reported to be obtained by using innovative chemical purification strategy, also called adduct purification. These high purities are often required for semiconductor industry uses.


Tellurium forms many compounds, but none that are commercially important.  They include:

Tellurous Acid (H2TeO2) Tellurium Tetrachloride (TeCl4)
Tellurium Dichloride (TeCl2) Tellurium Trioxide (TeO3)
Tellurium Monoxide (TeO) Sodium Telluride (Na2Te)

Tellurium is in the same series as Sulfur and Selenium and forms similar compounds.   A compound with metal or Hydrogen and similar ions is called a Telluride.   Gold and Silver Tellurides are considered good ores.  Compounds with tellurate ions complexes TeO42- or TeO66- are known as Tellurates.  Also Tellurites, TeO32-.  Also Tellurols –TeH, named with prefix tellanyl- or suffix -tellurol.


There are 30 known isotopes of Tellurium with atomic masses that range from 108 to 137. Naturally found tellurium consists of eight isotopes (listed in the table to the right); three of them are observed to be radioactive. 128Te has the longest known half-life, 2.21024 years, among all radioactive isotopes. Tellurium is the first element which can undergo Alpha Decay, with isotopes 106Te to 110Te being able to undergo this mode of decay.

atom.gif (700 bytes)

Isotope Atomic Mass Half-Life
Te106 105.938 60 us
Te107 106.935 3.1 ms
Te108 107.929 2.1 seconds
Te109 108.9275 4.6 seconds
Te110 109.9224 18.6 seconds
Te111 110.9211 19.3 seconds
Te112 111.917 2 minutes
Te113 112.916 1.7 minutes
Te114 113.912 15.2 minutes
Te115 114.912 5.8 minutes
Te116 115.9084 2.49 hours
Te117 116.9086 62 minutes
Te118 117.9058 6 days
Te119 118.9064 16.03 hours
Te120 119.904 Stable
Te121 120.9049 16.78 days
Te122 121.9031 Stable
Te123 122.9043 >1E 13 years
Te124 123.9028 Stable
Te125 124.9044 Stable
Te126 125.9033 Stable
Te127 126.9052 9.35 hours
Te128 127.9045 2.2E 24 years
Te129 128.9066 69.6 minutes
Te130 129.9062 7.9E 20 years
Te131 130.9085 25 minutes
Te132 131.9085 3.204 days
Te133 132.9109 12.5 minutes
Te134 133.9115 41.8 minutes
Te135 134.9165 19 seconds
Te136 135.9201 17.5 seconds
Te137 136.925 2.49 seconds
Te138 137.929 1.4 seconds
Te139 138.935 >150 ns
Te140 139.939 >150 ns
Te141 140.944 >150 ns
Te142 141.949 >150 ns


40px-Skull_and_crossbones.svg.jpg (1420 bytes) Tellurium and Tellurium compounds should be considered to be mildly toxic and need to be handled with care.  Acute poisoning is rare.  Tellurium is not reported to be carcinogenic.

Humans exposed to as little as 0.01 mg/m3 or less in air develop "Tellurium Breath", which has a garlic-like odor.  The garlic odor that is associated with human intake of Tellurium compounds is caused from the Tellurium being metabolized by the body. When the body metabolizes Tellurium in any oxidation state, the Tellurium gets converted into Dimethyl Telluride, (CH3)2Te.  Dimethyl Telluride is volatile and produces the garlic-like smell.

atom.gif (700 bytes)

Tellurium Data


Atomic Structure

Atomic Radius (): 1.42
Atomic Volume cm3/mol : 20.5cm3/mol
Covalent Radius: 1.36
Crystal Structure: Hexagonal
Ionic Radius: 0.97

Chemical Properties

Electrochemical Equivalents: 1.1902 g/amp-hr
Electron Work Function: 4.95eV
Electronegativity: 2.1 (Pauling); 2.01 (Allrod Rochow)
Heat of Fusion: 17.49 kJ/mol
Incompatibilities: Oxidizers, Chlorine, Cadmium
First Ionization Potential: 9.009
Second Ionization Potential: 18.6
Third Ionization Potential: 27.96
Valence Electron Potential: 59
Ionization Energy (eV): 9.010 eV

Physical Properties

Atomic Mass Average: 127.6
Boiling Point: 1261K, 988C, 1810F
Melting Point: 722.8K, 449.65C, 841.37F
Heat of Vaporization: 52.55 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 16.75E-6
Electrical Conductivity: 2.0E-6 106/cm
Thermal Conductivity: 0.0235 W/cmK
Density: 6.24 g/cm3 @ 300K
Enthalpy of Atomization: 190.4 kJ/mole @ 25C
Enthalpy of Fusion: 17.49 kJ/mole
Enthalpy of Vaporization: 50.6 kJ/mole
Flammability Class: Combustible Solid
Molar Volume: 20.42 cm3/mole
Optical Refractive Index: 1.000991
Relative Gas Density (Air=1): unknown
Specific Heat: 0.2 J/gK
Vapor Pressure: 23.1 Pa @ 449.65C
Estimated Crustal Abundance: 110-3 milligrams per kilogram
Estimated Oceanic Abundance: unknown

(L. tellus, earth) Discovered by Muller von Reichenstein in 1782; named by Klaproth, who isolated it in 1798.  Tellurium is occasionally found native, but is more often found as the telluride of Gold (Calaverite), and combined with other metals.  It is recovered commercially from the anode muds produced during the electrolytic refining of blister copper.  The U.S., Canada, Peru, and Japan are the largest Free World producers of the element.  Crystalline Tellurium has a silvery-white appearance, and when pure exhibits a metallic luster.  It is brittle and easily pulverized.   Amorphous Tellurium is found by precipitating Tellurium from a solution of Telluric or Tellurous Acid, (Te(OH)6).  Whether this form is truly amorphous, or made of minute crystals, is open to question.  Tellurium is a p-type semiconductor, and shows greater conductivity in certain directions, depending on alignment of the atoms.  Its conductivity increases slightly with exposure to light.  It can be doped with Silver, Copper, Gold, Tin, or other elements.  In air, Tellurium burns with a greenish-blue flames, forming the dioxide.  Molten Tellurium corrodes Iron, Copper, and stainless steel.   Tellurium and its compounds are probably toxic and should be handled with care. Workmen exposed to as little as 0.01 mg/m3 of air, or less, develop "Tellurium Breath," which has a garlic-like odor.  Thirty isotopes of tellurium are known, with atomic masses ranging from 108 to 137.  Natural Tellurium consists of eight isotopes. Tellurium improves the machinability of Copper and stainless steel, and its addition to lead decreases the corrosive action of Sulfuric Acid, H2SO4, on Lead and improves its strength and hardness.   Tellurium is used as a basic ingredient in blasting caps, and is added to cast Iron for chill control. Tellurium is used in ceramics.  Bismuth Telluride (Bi2Te3) has been used in thermoelectric devices. Tellurium costs about $100/lb, with a purity of about 99.5%.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond

Tellurium was discovered by Franz Joseph Mller von Reichenstein, a Romanian mining official, in 1782.  Reichenstein was the chief inspector of all mines, smelters and saltworks in Transylvania.  He also had an interest in chemistry and extracted a new metal from an ore of Gold, known as Aurum Album, which he believed was Antimony.  He shortly realized that the metal he had produced wasn't antimony at all, but a previously unknown element.  Reichenstein's work was forgotten until 1798 when Martin Heinrich Klaproth, a German chemist, mentioned the substance in a paper.   Klaproth named the new element Tellurium but gave full credit for its discovery to Reichenstein.