Tellurium

Atomic Number:

52

Melting Point: 449.5 ºC
Atomic Symbol: Te Boiling Point:  988 ºC
Atomic Weight: 127.60 amu Density: 6240 kg/m 3
Atomic Radius:

143.2 pm

Oxidation States: 6, 4, -2
Covalent Radius: 135 pm Electron Configuration: [Kr]5s24d105p4
van der Waals Radius:

206 pm

State of Matter: solid (nonmagnetic)

History

(L. tellus: earth) Discovered by Muller von Reichenstein in 1782; named by Klaproth, who isolated it in 1798.

Properties

Crystalline tellurium has a silvery-white appearance, and when pure it 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. 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.

Sources

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 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.

Uses

It is mostly used in alloys with other metals. 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 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 has been used in thermoelectric devices.

It has potential applications in cadmium telluride solar panels. Some of the highest efficiencies for solar cell electric power generation have been obtained by using this material, but this application has not yet caused demand to increase significantly.

Isotopes

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

Hazards

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.