Tellurium

Electron Configuration: [Kr] 4d¹⁰ 5s² 5p⁴
 
Properties:

Name of Element: Tellurium
Element Classification: Semimetallic
Symbol: Te
Atomic Number: 52
Atomic Mass: 127.6 amu
Melting Point (°K): 722.7
Boiling Point (°K):  1263
Crystal Structure: Hexagonal
Density (g/cm3): 6.24
Specific Heat (@20°C J/g mol): 0.201
Fusion Heat (kJ/mol): 17.91
Evaporation Heat (kJ/mol): 49.8
Pauling Negativity Number: 2.1
First Ionizing Energy (kJ/mol): 869
Oxidation States: 6, 4, 2
Lattice Structure: Hexagonal
Lattice Constant (Å): 4.450

Description:  Crystalline Tellurium has a silvery-white appearance, and exhibits a metallic lustre when pure.  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.  Tellurium can be doped with silver, copper, gold, tin, or other elements.

Separation:  Most Tellurium is made as a byproduct of copper refining.  The extraction technology is highly complex and the specific method selected depends upon the other trace compounds and elements present along with Tellurium.  Typically, the first step  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

References:

"Tellurium",  Los Alamos National Laboratory, 2003-12-15, http://periodic.lanl.gov/elements/52.html.

Tellurium Basic Atomic Spectroscopic Data, National Institute of Standards and Technology, http://physics.nist.gov/PhysRefData/Handbook/Tables/telluriumtable1.htm

Hudgens, S.; Johnson, B. (2004). "Overview of Phase-Change Chalcogenide Nonvolatile Memory Technology". Material Research Society Bulletin 29 (11): 1–4. http://www.engr.sjsu.edu/sgleixner/mate270/LectureNotes/Hudgens_MRS.pdf. 

"Mineral Yearbook 2007: Selenium and Tellurium". United States geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/selenium/myb1-2007-selen.pdf.  

"Ultra-pure organotellurium precursors for the low temperature MOVPE growth of II/VI compound semiconductors". Journal of Crystal Growth 93: 744–749. 1988. doi:10.1016/0022-0248(88)90613-6

Farivar, Cyrus (2006-10-19). "Panasonic says that its 100GB Blu-ray discs will last a century