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Tellurium
Atomic Number: 52 Atomic radius: 206 hours (Van der Waals)
Atomic Symbol: Te Melting point: 449.5 ° C
Atomic Weight: 127.60 Boiling point: 988 ° C
Electronic configuration: [Kr] 5s 2 4d10 5p 4 Oxidation States: 6, 4, -2

History
From the Latin word elit, land. Discovered by Müller von Reichenstein in 1782, named by Klaproth, who isolated it in 1798.

Sources
Tellurium isoccasionally found native, but is more often as the gold telluride (calaverite), and combined with other metals. It is recovered commercially from the anode sludge produced during the electrolyticrefining of blister copper. The U.S., Canada, Peru and Japan are the largest producers in the world free of the element.

Properties
Crystalline tellurium has a silvery white appearance, and in a purestate provides a metallic sheen. Is brittle and easily pulverized. Amorphous tellurium is tellurium by precipitation from a solution of telluric acid or teluroso. If this form is truly amorphous, or madeof minute crystals, is an open question. Tellurium is a p-type semiconductor, and shows a greater conductivity in certain directions, depending on the alignment of atoms.

Its conductivityincreases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. In air, tellurium burns with a flame greenish blue, which forms carbon dioxide. Molten telluriumcorrodes iron, copper and stainless steel.

Manipulation
Tellurium and its compounds are probably toxic and should be handled with care. Workers exposed to as little as 0.01 mg / m 3 of air, orless, develop "tellurium breath", which has a garlic-like odor.

Isotopes
Thirty isotopes of tellurium are known, with atomic masses ranging from 108 to 137. Natural tellurium consists of eightisotopes.

Use
Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and...