Hello everyone. In this video, I would like to tell you about one of the most treacherous elements
that will make anyone who dares to hold it just for a few seconds in his hands
regret his decision.
In the periodic table of chemical elements, Tellurium is right below Selenium in group 16
and, in contrast to the elements preceding it,
Tellurium belongs to the semimetals.
This element is very scarce in Earth's crust
and its rarity is compared to that of platinum.
Tellurium is so rare because, during the first stages of Earth's formation,
its compounds reacted with water, forming volatile hydrogen telluride
which has easily vanished into open space through earth's atmosphere.
Today tellurium is obtained when copper electroplating produces byproducts
in the form of tellurides of precious metals
which, later on, are reduced to metallic tellurium.
After refining, pieces of this metal look very similar to pieces of any other metal,
although, holding tellurium in the hands for just a few seconds is enough to make sure it is tellurium.
The smallest bits of this element combines with oil in our fingers and gets inside the organism.
This is not necessarily deadly, but it's very unpleasant to those around you
because, inside your body, tellurium metabolizes into dimethyl telluride.
Since all tellurium compounds have a disgusting smell,
any person who comes into contact with tellurium gets nasty garlic breath
which can last up to a few weeks.
That is why lots of workers who work at tellurium-producing factories
suffer from garlic-related problems
whereas chemists who work with tellurium compounds
have certain difficulties when communicating with other people.
In spite of this treacherous property of tellurium,
let us continue considering its properties.
Tellurium can exist in two forms:
in crystalline form - the one you have already seen
and its amorphous form
which looks like black powder.
Crystalline tellurium melts at 450 degrees Celsius.
and, at the same time, it also oxidizes into whitish tellurium dioxide.
It is worthy of note that mixed tellurium oxide is used in one of compact discs' rewritable layers.
That is why I think every one of us has indirectly contacted with this element at least once in life.
Besides, crystalline tellurium comes into a weak reaction with concentrated sulfuric acid
and forms tetratellurium decaoxotrisulfate(VI).
However, if you mix amorphous tellurium with concentrated sulfuric acid
instead of crystalline tellurium and heat it up,
the reaction will produce the same chemical of a saturated red color
which is the result of tellurium polycations 4+ in the solution.
It is also of note that when water is added to such a red solution
its color immediately disappears because of the decomposition of red components.
Judging by the bubbles, amorphous tellurium doesn't dissolve that well in sulfuric acid
but still it does dissolve, forming water-soluble compounds.
Tellurium also actively reacts with diluted nitric acid just as well as with sulfuric acid.
Besides, many compounds of tellurium are toxic to humans.
However, some bacteria (for instance, bacteria causing diphtheria)
can be detected in a special medium for bacteria with tellurium oxide.
This helps to detect diseases, and shows the right treatment.
Besides acids, tellurium also reacts with some metals.
For instance, it reacts with sodium upon heating.
This reaction produces sodium tellurides: a useful chemical for organic synthesis.
If cadmium is used instead of sodium in this experiment,
the obtained cadmium telluride comes out as a more useful chemical.
It is used for making a new type of thin-film solar cells
which turn out to be cheaper to make, and require fewer materials.
However, because of its relatively low efficiency, this type of solar cell is still underway
but, because of its low manufacturing cost, it takes less than a year for it to produce enough energy
to recover the cost.
Apart from that, germanium and tellurium compounds are used
to make new types of PRAM random access memory
the speed of which is a few thousand times faster than the speed of hard-disk drives.
Now, such random access memory is sold by such brands as Optane and Quantics.
To sum up, we can say that tellurium is quite a treacherous element
but, when it's dealt with carefully, incredible things can be made from it
such as efficient solar cells and superfast random access memory.
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