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Wednesday, 17 July 2013

Silicon Element Facts

Discovery of Silicon

Dr. Doug Stewart
Quartz (crystalline silicon dioxide) has been known to people for many thousands of years. Flint is a form of quartz, and tools made from flint were in everyday use in the stone age.
In 1789, the French chemist Antoine Lavoisier proposed that a new chemical element could be found in quartz. This new element, he said, must be very abundant. (1) He was right, of course. Silicon accounts for 28% of the weight of Earth’s crust.
It is possible that in England, in 1808, Humphry Davy isolated partly pure silicon for the first time, but he did not realize it. (2)
In 1811, French chemists Joseph L. Gay-Lussac and Louis Jacques Thénard may also have made impure silicon by reacting potassium with silicon tetrafluoride to produce a reddish brown solid which was probably amorphous silicon. They did not, however, attempt to purify this new substance. (3), (4)
In 1824, Swedish chemist Jöns Jakob Berzelius produced a sample of amorphous silicon, a brown solid, by reacting potassium fluorosilicate with potassium and purifying the product with repeated washing. He named the new element silicium. (3), (4)
At that time the concept of semiconductors lay a century in the future. Unaware that such materials existed and that silicon was an excellent example of a semiconductor, scientists debated whether the new element should be classed as a metal or a nonmetal.
Berzelius believed it was a metal, while Humphry Davy thought it was a nonmetal. (5)   The problem was that the new element was a better conductor of electricity than nonmetals, but not as good a conductor as a metal.
Silicon was given its name in 1831 by Scottish chemist Thomas Thomson. He retained part of Berzelius’s name, from ‘silicis,’ meaning flint. He changed the element’s ending to on because the element was more similar to nonmetals boron and carbon than it was to metals such as calcium and magnesium. (Silicis, or flint, was probably our first use of silicon dioxide. (4), (6))
In 1854, Henri Deville produced crystalline silicon for the first time. He did this by electrolyzing an impure melt of sodium aluminum chloride to produce aluminum silicide. The aluminum was removed with water, leaving silicon crystals. (4)
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