Tellurium hexafluoride
Encyclopedia
Tellurium hexafluoride is the oldest known fluoride
of tellurium. It is a colorless, highly toxic gas with an extremely unpleasant smell.
gas over tellurium metal at 150 °C. Below this temperature a mixture of lower fluorides form, including tellurium tetrafluoride
and ditellurium decafluoride
. It can also be prepared by passing fluorine gas over TeO3 or indirectly by reacting TeO2 with SeF4 to produce TeF4 and then heating TeF4 in excess of 200 °C to make TeF6 and Te.
and selenium
analogs. It is less volatile
, however, due to the increase in molecular weight. At temperatures below −38 °C, tellurium hexafluoride condenses to a volatile white solid.
analog, tellurium hexafluoride is not chemically inert
. This can be attributed to the greater availability of the d orbitals and perhaps the availability of the f orbitals which neither sulfur or selenium have access to. TeF6 is hydrolyzed in water to H6TeO6 and reacts with Te below 200 °C.
-like odour. This garlic odour is also present in sweat
and urine
. Other symptoms of tellurium exposure include headache
, dyspnea
, weakness, bluish-black markings on finger
s, neck
, face
and gums, metallic taste in the mouth and skin rash. Death may occur from pulmonary edema
. People exposed to tellurium compounds should be removed from the area and seek medical attention.
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
of tellurium. It is a colorless, highly toxic gas with an extremely unpleasant smell.
Preparation
Tellurium hexafluoride is most commonly prepared by passing fluorineFluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
gas over tellurium metal at 150 °C. Below this temperature a mixture of lower fluorides form, including tellurium tetrafluoride
Tellurium tetrafluoride
Tellurium tetrafluoride, TeF4, is a stable, white, hygroscopic crystalline solid and is one of two fluorides of tellurium. The other binary fluoride is tellurium hexafluoride. The widely reported Te2F10 has been shown to be F5TeOTeF5 There are other tellurium compounds that contain fluorine, but...
and ditellurium decafluoride
Ditellurium decafluoride
Ditellurium decafluoride was widely reported in the literature but what was believed to be Te2F10 has been shown to be F5TeOTeF5. An account as to how this error occurred was made by P.M. Watkin....
. It can also be prepared by passing fluorine gas over TeO3 or indirectly by reacting TeO2 with SeF4 to produce TeF4 and then heating TeF4 in excess of 200 °C to make TeF6 and Te.
Properties
Tellurium hexafluoride is a highly symmetric octahedral molecule. Its physical properties resemble the sulfurSulfur hexafluoride
Sulfur hexafluoride is an inorganic, colorless, odorless, and non-flammable greenhouse gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in...
and selenium
Selenium hexafluoride
Selenium hexafluoride is the inorganic compound with the formula SeF6. It is a colourless gas described as having a "repulsive" odor. It is not widely encountered and has no commercial applications.-Structure, preparation, and reactions:...
analogs. It is less volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...
, however, due to the increase in molecular weight. At temperatures below −38 °C, tellurium hexafluoride condenses to a volatile white solid.
Reactivity
Unlike the sulfurSulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
analog, tellurium hexafluoride is not chemically inert
Inert
-Chemistry:In chemistry, the term inert is used to describe a substance that is not chemically reactive.The noble gases were previously known as inert gases because of their perceived lack of participation in any chemical reactions...
. This can be attributed to the greater availability of the d orbitals and perhaps the availability of the f orbitals which neither sulfur or selenium have access to. TeF6 is hydrolyzed in water to H6TeO6 and reacts with Te below 200 °C.
Health Hazards
People exposed to tellurium compounds exhibit "tellurium breath", which has a garlicGarlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
-like odour. This garlic odour is also present in sweat
SWEAT
SWEAT is an OLN/TSN show hosted by Julie Zwillich that aired in 2003-2004.Each of the 13 half-hour episodes of SWEAT features a different outdoor sport: kayaking, mountain biking, ice hockey, beach volleyball, soccer, windsurfing, rowing, Ultimate, triathlon, wakeboarding, snowboarding, telemark...
and urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
. Other symptoms of tellurium exposure include headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
, dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
, weakness, bluish-black markings on finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
s, neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
, face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
and gums, metallic taste in the mouth and skin rash. Death may occur from pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
. People exposed to tellurium compounds should be removed from the area and seek medical attention.
Literature
- W.C. Cooper; Tellurium, Van Nostrand Reinhold Company, New York, USA, 1971.
- K.W. Bagnall; The Chemistry of Selenium, Tellurium and Polonium, Elsevier Publishing, New York, 1966.
- R.T. Sanderson; Chemical Periodicity, Reinhold, New York, USA, 1960.
- N.N. Greenwood and A. Earnshaw; Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
- F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann; Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
- G.J. Hathaway, N.H. Proctor; Chemical Hazards of the Workplace, 5th edition, Wiley-Interscience, New Jersey, 2004.