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Se

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Te

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Element Fact
Selenium is an essential trace element in the diets that acts as antioxidants.

Tellurium, Te

tin sample

Atomic number: 52
Atomic mass: 127.60(3)
Natural abundance: 0.002 ppm
Isotopes:
120Te (119.90402) - 0.096%
122Te (121.903047) - 2.603%
123Te (122.904273) - 0.908%
124Te (123.902819) - 4.816%
125Te (124.904425) - 7.139%
126Te (125.903306) - 18.95%
128Te (127.904461) - 31.69%
130Te (129.906223) - 33.80%

History and Production

From Latin tellus, meaning earth. It was first isolated by F.J. Müller von Reichenstein in 1782. The name was actually given by M.H. Klaproth. It is recovered commercially from the anode slime deposited during electrolytic refinement of copper. It is mainly used in iron and steel production and also as a curing agent in the rubber industry. Addition to lead improves the mechanical strength and resistant to sulfuric acid attack. It is also used for making semiconductor devices.

Physical Data

Crystalline tellurium has a silvery-white appearance. It is brittle and easily pulverized. Tellurium is a p-type semiconductor and, depends on the alignment of atoms, show greater electrical conductivity in certain directions. Tellurium is quite rare, it can occasionally found native but mainly occur together with sulfides ores of other metals such as copper, nickel and cobalt.

Interatomic distance: 286.4 pm
Melting point: 449.51°C
Boiling point: 988°C
Thermal conductivity/Wm-1K-1: 2.35 (27°C)
Density/kgm-3: 6240 (20°C), 5797 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 196.7 kJ/mol
Gibbs free energy of formation: 157.1 kJ/mol
Entropy: 182.7 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Kr] 4d10 5s2 5p4
Term symbol: 3P2
Electron affinity: 190.1534 kJ/mol   Electronegativity (Pauline): 2.10
Ionization energy (first, second, third): 869.295, 1794.63, 2697.73 kJ/mol

Chemical properties


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