Tellurium: the essentials
Crystalline tellurium has a silvery-white appearance, and exhibits a metallic lustre when pure (see above). It is brittle and easily pulverised. Tellurium is a p-type semiconductor, and shows varying conductivity with crystal alignment. Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements.
Humans exposed to as little as 0.01 mg m-3 in air, or less, develop "tellurium breath", which has a garlic-like odour.
Tellurium: historical information
Tellurium was discovered in gold ores by Franz Joseph Mδller von Reichenstein, the chief inspector of mines in Trannsylvania in 1782. However tellurium was named by M. Klaproth, who isolated it in 1798, after he continued Mδller von Reichenstein's work.
Tellurium around us Read more »
Tellurium has no biological role. All tellurium compounds are highly toxic.
Tellurium is occasionally found as the free element, but is more often found as gold telluride (calaverite), and combined with other metals in the USA, Canada, Peru and Japan.
|Location||ppb by weight||ppb by atoms||Links|
|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 722.66 [449.51 °C (841.12 °F)] K
- Boiling point: 1261 [988 °C (1810 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of tellurium is: trigonal.
Tellurium: orbital properties Read more »
Tellurium atoms have 52 electrons and the shell structure is 220.127.116.11.6. The ground state electronic configuration of neutral Tellurium is [Kr].4d10.5s2.5p4 and the term symbol of Tellurium is 3P2.
- Pauling electronegativity: 2.1 (Pauling units)
- First ionisation energy: 869.3 kJ mol‑1
- Second ionisation energy: 1790 kJ mol‑1
Isolation: it is not usually necessary to make tellurium in the laboratory as it is commercially available. While there are some tellurium ores, most tellurium is made as a byproduct of copper refining. Extraction is complex since the method emplyed will depend upon what other compounds or elements are present. The first step usually involves an oxidation in the presence of sodium carbonate (soda ash).
Cu2Te + Na2CO3 + 2O2 → 2CuO + Na2TeO3 + CO2
The tellurite Na2TeO3 is acidified with sulphuric acid and the tellurium precipitates out as the dioxide (leaving and selenous acid, H2SeO3, in solution). Tellurium is liberated from the dioxide by dissolving in sodium hydroxide, NaOH, and electroytic reduction.
TeO2 + 2NaOH → Na2TeO3 + H2O → Te + 2NaOH + O2
Tellurium isotopes Read more »
Tellurium has eight stable isotopes (Te-120 and Te-123 are usually considered stable because of their long half lives) and many of them have a medical application. Te-120 is used for the production of I-120g which has an application as a PET and Beta emitting isotope. Te-122 is used in the production of the radioisotope I-122 which is used in gamma imaging. Te-123 is used for the production of radioactive I-123 which is used in thyroid imaging. Te-124 is used for the production of both I-123 and the PET isotope I-124. Finally, Te-130 is used in the research into double Beta decay.
|120Te||119.904048 (21)||0.09 (1)||0|
|122Te||121.903050 (3)||2.55 (12)||0|
|123Te||122.9042710 (22)||0.89 (3)||1/2||-0.73679|
|124Te||123.9028180 (18)||4.74 (14)||0|
|125Te||124.9044285 (25)||7.07 (15)||1/2||-0.88828|
|126Te||125.9033095 (25)||18.84 (25)||0|
|128Te||127.904463 (4)||31.74 (8)||0|
|130Te||129.906229 (5)||34.08 (62)||0|