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Name, Symbol, NumberTellurium, Te, 52
Series metalloids
Group, Period, Block16 (VIA), 5 , p
Density, Hardness 6240 kg/m3, 2.25
Appearance silvery lustrous gray
Atomic Properties
Atomic weight 127.60 amu
Atomic radius (calc.) 140 (123)pm
Covalent radius 135 pm
van der Waals radius 206 pm
Electron configuration [Kr]4d10 5s2 5p4
e- 's per energy level2, 8, 18, 18, 6
Oxidation states (Oxide) 2, 4, 6 (mildly acidic)
Crystal structure Hexagonal
Physical Properties
State of matter Solid (nonmagnetic)
Melting point 722.66 K (841.12 F)
Boiling point 1261 K (1810 F)
Molar volume 20.46 ×10-3 m3/mol
Heat of vaporization 52.55 kJ/mol
Heat of fusion 17.49 kJ/mol
Vapor pressure 23.1 Pa at 272.65 K
Speed of sound 2610 m/s at 293.15 K
Electronegativity 2.1 (Pauling scale)
Specific heat capacity 202 J/(kg*K)
Electrical conductivity 200 /m ohm
Thermal conductivity 2.35 W/(m*K)
1st ionization potential 869.3 kJ/mol
2nd ionization potential 1790 kJ/mol
3rd ionization potential 2698 kJ/mol
4th ionization potential 3610 kJ/mol
5th ionization potential 5668 kJ/mol
6th ionization potential 6820 kJ/mol
7th ionization potential 13200 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
120Te0.096%Te is stable with 68 neutrons
122Te2.603%Te is stable with 70 neutrons
123Te0.908>1 E13 y Epsilon0.051123Sb
124Te4.816%Te is stable with 72 neutrons
125Te7.139%Te is stable with 73 neutrons
126Te18.952%Te is stable with 74 neutrons
128Te31.6872.2 E24 yBeta-0.867128Xe
130Te33.7997.9 E20 y Beta-2.528130Xe
SI units & STP are used except where noted.
Tellurium is a chemical element in the periodic table that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks like tin, tellurium is chemically related to selenium and sulfur. This element is primarily used in alloys and as a semiconductor.

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Notable Characteristics Tellurium is a relatively rare element, in the same chemical family as oxygen, sulfur, selenium, and polonium (the chalcogens).

When crystalline, tellurium is silvery-white and when it is in its pure state it has a metallic luster. This is a brittle and easily pulverized metalloid. Amorphous tellurium is found by precipitating it from a solution of tellurous or telluric acid. However, there is some debate whether this form is really amorphous or made of minute crystals. Tellurium is a p-type semiconductor that shows a greater conductivity in certain directions which depends on atomic alignment.

Chemically related to selenium and sulfur, the conductivity of this element increases slightly when exposed to light. It can be doped with copper, gold, silver, tin, or other metals. Tellurium has a greenish-blue flame when burned in normal air and forms tellurium dioxide as a result. When in its molten state, tellurium is corrosive to copper, iron, and stainless steel. Applications It is mostly used in alloys with other metals. It is added to lead to improve its strength, durability and to decreases the corrosive action of sulfuric acid. When added to stainless steel and copper it makes these metals more workable. Other uses;

  • It is alloyed into cast iron for chill control.
  • Used in ceramics.
  • Bismuth telluride has found use in thermoelectric devices.

Tellurium is also used in blasting caps[?], and 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. History Tellurium (Latin tellus meaning "earth") was discovered in 1782 by Franz Joseph Muller von Reichstein[?] in Romania. In 1798 it was named by Martin Heinrich Klaproth[?] who earlier isolated it.

The 1960s brought growth in thermoelectric applications for tellurium, as well as its use in free-machining steel, which became the dominant use. Occurrence Tellurium is sometimes found in its native form, but is more often found as the telluride of gold (calaverite[?]), and combined with other metals. The principal source of tellurium is from anode muds produced during the electrolytic refining of blister copper.

Commercial-grade tellurium, which is not toxic, is usually marketed as minus 200-mesh powder but is also available as slabs, ingots, sticks, or lumps. The yearend price for tellurium in 2000 was US$ 14 per pound. Compounds Tellurium is in the same series as sulfur and selenium and forms similar compounds. A compound with metal or hydrogen and similar ions is called a telluride. Gold and silver tellurides are considered good ore. Isotopes There are 30 known isotopes of tellurium with atomic masses that range from 108 to 137. Naturally found tellurium consists of eight isotopes (listed in the table to the right) . Precautions Humans exposed to as little as 0.01 mg/m3 or less in air develop "tellurium breath", which has a garlic-like odor. Tellurium and tellurium compounds should be considered to be toxic and need to be handled with care.

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