Silicon is the atomic number 14 element of the third period of the carbon family, and because of that, it has several carbon-like properties. For example, it is a hard solid, whose crystal structure is similar to that of diamond, which is formed only by bonds between carbons. Its chemical reactions are also similar to this element.
This solid has a gray color and a metallic shine, and its name comes from flint or silicis, which means "hard stone".
It is very abundant in nature, in the entire universe he is the 7th most abundant, standing behind the following elements: hydrogen, helium, neon, oxygen, nitrogen and carbon. In the Earth's crust, it is the second in greatest quantity (27.7%),second only to oxygen.
However, it is never found naturally in isolated form, it is always combined with some other element. For this reason, it was first prepared in the laboratory, in 1824, by the Swedish chemist Jöns Jacob Berzelius, by heating silicon tetrafluoride with potassium.
He is present in practically all sand, rock, clay and soil
. It can also be found in all natural waters, in the atmosphere (as dust), in many plants and in the skeletons, tissues and body fluids of some animals.When combined with oxygen, it forms the silica (silicon dioxide - SiO2), and when it is combined with oxygen and other elements, it forms silicates, the main ones being the quartz, asbestos, zeolite and mica.
The name "asbestos" comes from greek asbestos, which means “non-combustible”, and is best known for its synonym "asbestos", which comes from latin asbestos, which means “incorruptible”. Asbestos is the generic name for the natural fibrous silicates found in the soil in more than 30 varieties, only 6 of which are of commercial interest. The two main groups of asbestos rocks are:
1. Streamers (white asbestos - 95%):consisting of chrysotile mineral (Mg3Yes2O5(OH)4);
2. Amphiboles (brown, blue and other asbestos - 5%):consisting of tremolite minerals (Ca2mg5Yes8O22(OH)2), amosite ((Fe, Mg, Ca) OSiO2. n H2O) and crocidolite (NaFe2(SiO3)3).
Because it has several important physicochemical properties, such as high mechanical resistance at high temperatures, being insulating, flexible, resisting the attack of acids, bacteria, alkalis, etc., this causes this fiber to be used in the manufacture of tiles, tanks, in various civil construction products and to thermally insulate machines and equipment. However, the use of asbestos causes a lot of controversy and is prohibited in several countries because the asbestos microlint can be absorbed into the lungs and cause a disease called silicosis, as well as other ailments for the body.
On an industrial scale, silicon is produced by the reaction of the oxide with coke. But to obtain an ultra-pure silicon, silane decomposition (SiH) is performed.4) or silicon tetrahalides at high temperatures.
This ultra-pure silicon is important for the manufacture of semiconductors for use in electronic equipment, such as:
- Diodes:electronic component that is an excellent conductor when subjected to voltage in the direct direction, but a poor conductor when subjected to voltage in the opposite direction;
- Transistors:electronic component that amplifies electrical signals;
- Microprocessors:electronic component that interprets a set of instructions and performs logical and mathematical operations.
With pure silicon it is possible to obtain extremely thin sheets, which are used in the production of chips with smaller and smaller dimensions, used in computer and other integrated circuits.
Silicon is used for this purpose because it has 4 electrons in its valence shell and its atoms combine to form crystals. At room temperature, these electrons gain enough energy to move freely around the crystal, leaving holes that can be filled by electrons from neighboring atoms. Thus, the gap moves from one atom to the other, continuously forming new pairs of electron-holes.
However, this does not make it a good conductor, because it has few free electrons, so it is called a semiconductor. It is with the combination of semiconductors that we obtain the electronic components mentioned above.
Since this element is the main raw material in the production of most circuits and chips electronics, a region located in California, United States, where an industrial center is concentrated with several information technology and computing companies, among others, it started to receive the name in Silicon Valley, in honor of that element.
A last important application of this element is as polymers of silicone, with its main chain made up of silicon atoms alternating with oxygen atoms. Of the silicone varieties, the most used today are dichlo-dimethyl-silane or dichloro-diphenyl-silane. To understand how their formation processes occur from silicon, read the text "Silicone - constitution and applications”.
By Jennifer Fogaça
Graduated in Chemistry