This is a list of the 118 chemical elements which have been identified as of 2021. A chemical element, often simply called an element, is a species of atoms which all have the same number of protons in their atomic nuclei (i.e., the same atomic number, or Z). Silicon (Atomic number 14) is an important element in electronics Forms of an Element Even though elements are all made from the same type of atoms, they can still come in different forms.
- Silicon Atomic Number Valency
- Silicon Atomic Number Name
- Silicon Atomic Number Electron Configuration
- Silicon 28 Atomic Number
- Silicon Atomic Number And Symbol
Overview
Silicon is a member of Group 14 (IVA) in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Silicon is also part of the the carbon family. Other carbon family elements include carbon, germanium, tin, and lead. Silicon is a metalloid, one of only a very few elements that have characteristics of both metals and non-metals.
Silicon is the second most abundant element in the Earth's crust, exceeded only by oxygen. Many rocks and minerals contain silicon. Examples include sand, quartz, clays, flint, amethyst, opal, mica, feldspar, garnet, tourmaline, asbestos, talc, zircon, emerald, and aquamarine. Silicon never occurs as a free element. It is always combined with one or more other elements as a compound.
SYMBOL
Si
ATOMIC NUMBER
14
ATOMIC MASS
28.0855
FAMILY
Group 14 (IVA)
Carbon
PRONUNCIATION
SIL-i-con
By the early 1800s, silicon was recognized as an element. But chemists had serious problems preparing pure silicon because it bonds (attaches) tightly to oxygen. It took chemists many years to find out how to separate silicon from oxygen. That task was finally accomplished in 1823 by Swedish chemist Jons Jakob Berzelius (1779-1848).
Silicon's most important application is in electronic equipment. Silicon is one of the best materials from which to make transistors and computer chips. The total weight of silicon used for this purpose is relatively small. Much larger amounts are used, for example, to make metal alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals.
Discovery and naming
/GettyImages-186451126-58c396e33df78c353cf8cd8a.jpg "Silicon atomic number 32")
In one sense, humans have always used silicon. Nearly every naturally occurring rock or mineral contains some silicon. So when ancient peoples built clay huts or sandstone temples, they were using compounds of silicon.
But no one thought about silicon as an element until the nineteenth century. Then, a number of chemists tried to separate silicon from the other elements with which it is combined in the earth. English scientist Sir Humphry Davy (1778-1829) developed a technique for separating elements that tightly bond to each other. He melted these compounds and passed an electric current through them. The technique was successful for producing free or elemental sodium, potassium, calcium, and a number of other elements for the first time. But he failed with silicon. (See sidebar on Davy in the calcium entry in Volume 1.)
Berzelius also tried to isolate silicon using a method similar to that of Davy's. He mixed molten (melted) potassium metal with a compound known as potassium silicon fluoride (K 2 SiF 6 ). The result was a new element—silicon.
Scottish chemist Thomas Thomson (1773-1852) suggested the name silicon, based on the Latin word for 'flint,' silex (or silids). He added the ending -on because the new element was so much like boron and carbon. Thus, the new element's name was accepted as silicon.
Some interesting studies were done on silicon over the next few years. German chemist Friedrich Wohler (1800-82) produced a series of compounds known as silanes. These compounds contain silicon, hydrogen, and, sometimes, other elements.
The simplest silane is silicon tetrahydride (SiH 4 ). This compound is also called silane.A group of compounds known as the siloxanes were produced at about the same time. The siloxanes are made up of silicon, oxygen, and an organic group. Organic compounds contain carbon.
Silanes and siloxanes were not discovered in the search for the answer to any practical question. Chemists were just curious about the kinds of compounds they could make with silicon. But many years later, chemists made some interesting discoveries. Both groups of compounds do have some very important practical uses. For example, the compounds known as silicones are a form of the siloxanes.
Physical properties
Silicon is a metalloid, an element with properties of both metals and non-metals. Silicon exists in two allotropic forms. Allotropes are forms of an element with different physical and chemical properties. One allotrope is in the form of shiny, grayish-black, needle-like crystals, or flat plates. The second allotrope has no crystal structure and usually occurs as a brown powder.
Silicon Atomic Number Valency
The melting point of silicon is 1,410°C (2,570°F) and the boiling point is 2,355°F (4,270°F). Its density is 2.33 grams per cubic centimeter. Silicon has a hardness of about 7 on the Mohs scale. The Mohs scale is a way of expressing the hardness of a material. It runs from 0 (for talc) to 10 (for diamond).
Silicon is a semiconductor. A semiconductor is a substance that conducts an electric current better than a non-conductor—like glass or rubber—but not as well as a conductor—like copper or aluminum. Semiconductors have important applications in the electronics industry.
Chemical properties
Silicon Atomic Number Name
Silicon is a relatively inactive element at room temperature. It does not combine with oxygen or most other elements. Water, steam, and most acids have very little affect on the element. At higher temperatures, however, silicon becomes much more reactive. In the molten (melted) state, for example, it combines with oxygen, nitrogen, sulfur, phosphorus, and other elements. It also forms a number of alloys very easily in the molten state.
Occurrence in nature
Silicon is the second must abundant element in the Earth's crust. Its abundance is estimated to be about 27.6 percent of the crust. It ranks second only to oxygen. Some authorities believe that more than 97 percent of the crust is made of rocks that contain compounds of silicon and oxygen.
Silicon has been detected in the Sun and stars. It also occurs in certain types of meteorites known as aerolites or 'stony meteorites.' Meteorites are rock-like chunks that fall to the Earth's surface from outside the Earth's atmosphere.
Silicon never occurs as a free element in nature. It always occurs as a compound with oxygen, magnesium, calcium, phosphorus, or other elements. The most common minerals are those that contain silicon dioxide in one form or another. These are known as silicates.
Silicon has been detected in the Sun and stars. It also occurs in certain types of meteorites.
Isotopes
There are three naturally occurring isotopes of silicon: silicon-28, silicon-29, and silicon-30. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.
Five radioactive isotopes of silicon are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.
None of the radioactive isotopes of silicon has any commercial use.
Extraction
Silicon is prepared by heating silicon dioxide with carbon. Carbon replaces the silicon in the compound. The silicon formed is 96 to 98 percent pure.
Many applications of silicon require a very pure product. Methods have been developed to produce silicon that is at least 99.97 percent pure silicon. This form of silicon is called hyper-pure silicon.
Uses
Perhaps the best known use of silicon is in electronic devices. Hyperpure silicon is used in transistors and other components of electronic devices. It is also used to make photovoltaic (solar) cells, rectifiers, and parts for computer circuits. A photovoltaic cell is a device that converts sunlight into electrical energy. A rectifier is an electrical device for changing one kind of electric current (alternating current, or AC) into another kind of electric current (direct current, or DC).
Almost without exception, all glass contains silicon dioxide.
The largest single use of silicon, however, is in making alloys. The most important silicon alloys are those made with iron and steel, aluminum, and copper. When silicon is produced, in fact, scrap iron and metal is sometimes added to the furnace. As soon as the silicon is produced, it reacts with iron and steel to form ferrosilicon. Ferrosilicon is an alloy of iron or steel and silicon. It is used for two major purposes. First, it can be
The aluminum industry uses large amounts of silicon in alloys. These alloys are used to make molds and in the process of welding. Welding is a process by which two metals are joined to each other. Alloys of silicon, aluminum, and magnesium are very resistant to corrosion (rusting). They are often used in the construction of large buildings, bridges, and transportation vehicles such as ships and trains.
Compounds
A number of silicon compounds have important uses. Silicon dioxide (sand) is used in the manufacture of glass, ceramics, abrasives, as a food additive, in water filtration systems, as an insulating material, in cosmetics and Pharmaceuticals (drugs), and in the manufacture of paper, rubber, and insecticides. Each
Another important compound is silicon carbide (SiC). Silicon carbide is also known as carborundum. It is one of the hardest substances known, with a hardness of about 9.5 on the Mohs scale. Carborundum is widely used as an abrasive, a powdery material used to grind or polish other materials. Carborundum also has refractory properties. A refractory material can withstand very high temperatures by reflecting heat. Refractory materials are used to line the inside of ovens used to maintain very high temperatures.
Silicon Atomic Number Electron Configuration
Another important silicon group is the silicones. The silicones have an amazing range of uses. These include toys (Silly Putty and Superballs), lubricants, weatherproof!ng materials, adhesives (glues), foaming agents, brake fluids, cosmetics, polishing agents, electrical insulation, materials to reduce vibration, shields for sensitive equipment, surgical implants, and parts for automobile engines.
Health effects
Silicon 28 Atomic Number
Information on the health effects of silicon is limited. Some studies show that silicon may be needed in very small amounts by plants and some animals. One study showed, for example, that chickens that did not receive silicon in their diet developed minor health problems. Overall, silicon probably has no positive or negative effects on human health.
Silicon Atomic Number And Symbol
However, a serious health problem called silicosis is associated with silicon dioxide (SiO 2 ). Silicon dioxide occurs in many forms in the earth. Ordinary sand is nearly pure silicon dioxide.
In some industries, sand is ground up into a very fine powder that gets into the air. As workers inhale the dust, it travels through their mouths, down their throats, and into their lungs. Silicon dioxide powder can block the tiny air passages in the lungs through which oxygen and carbon dioxide pass. When this happens, silicosis results.
Silicosis is similar to pneumonia. The person finds it difficult to breathe. The longer one is exposed to silicon dioxide dust, the worst the problem gets. In the worst cases, silicosis results in death because of the inability to breathe properly.
Silicon is a chemical element in the periodic table that has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon. It is the second most abundant element in the Earth's crust, making up 25.7% of it by weight. It occurs in clay, feldspar, granite, quartz and sand, mainly in the form of silicon dioxide (also known as silica) and silicates (compounds containing silicon, oxygen and metals). Silicon is the principal component of glass, cement, ceramics, most semiconductor devices, and silicones, the latter a plastic substance often confused with silicon.
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| General | |||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Name, Symbol, Number | silicon, Si, 14 | ||||||||||||||||||||||||||||||
| Series | metalloid | ||||||||||||||||||||||||||||||
| Group, Period, Block | 14 (IVA), 3, p | ||||||||||||||||||||||||||||||
| Density, Hardness | 2330 kg/m3, 6.5 | ||||||||||||||||||||||||||||||
| Appearance | dark grey, bluish tinge | ||||||||||||||||||||||||||||||
| Atomic properties | |||||||||||||||||||||||||||||||
| Atomic weight | 28.0855 amu | ||||||||||||||||||||||||||||||
| Atomic radius (calc.) | 110 pm (111 pm) | ||||||||||||||||||||||||||||||
| Covalent radius | 111 pm | ||||||||||||||||||||||||||||||
| van der Waals radius | 210 pm | ||||||||||||||||||||||||||||||
| Electron configuration | [Ne]3s2 3p2 | ||||||||||||||||||||||||||||||
| e- 's per energy level | 2, 8, 4 | ||||||||||||||||||||||||||||||
| Oxidation states (Oxide) | 4 (amphoteric) | ||||||||||||||||||||||||||||||
| Crystal structure | cubic face centered | ||||||||||||||||||||||||||||||
| Physical properties | |||||||||||||||||||||||||||||||
| State of matter | solid (nonmagnetic) | ||||||||||||||||||||||||||||||
| Melting point | 1687 K (2577 °F) | ||||||||||||||||||||||||||||||
| Boiling point | 3173 K (5252 °F) | ||||||||||||||||||||||||||||||
| Molar volume | 12.06 ×10-6 m3/mol | ||||||||||||||||||||||||||||||
| Heat of vaporization | 384.22 kJ/mol | ||||||||||||||||||||||||||||||
| Heat of fusion | 50.55 kJ/mol | ||||||||||||||||||||||||||||||
| Vapor pressure | 4.77 Pa at 1683 K | ||||||||||||||||||||||||||||||
| Speed of sound | __ m/s at __ K | ||||||||||||||||||||||||||||||
| Miscellaneous | |||||||||||||||||||||||||||||||
| Electronegativity | 1.90 (Pauling scale) | ||||||||||||||||||||||||||||||
| Specific heat capacity | 700 J/(kg*K) | ||||||||||||||||||||||||||||||
| Electrical conductivity | 2.52 10-4/m ohm | ||||||||||||||||||||||||||||||
| Thermal conductivity | 148 W/(m*K) | ||||||||||||||||||||||||||||||
| 1st ionization potential | 786.5 kJ/mol | ||||||||||||||||||||||||||||||
| 2nd ionization potential | 1577.1 kJ/mol | ||||||||||||||||||||||||||||||
| 3rd ionization potential | 3231.6 kJ/mol | ||||||||||||||||||||||||||||||
| 4th ionization potential | 4355.5 kJ/mol | ||||||||||||||||||||||||||||||
| 5th ionization potential | 16091 kJ/mol | ||||||||||||||||||||||||||||||
| 6th ionization potential | 19805 kJ/mol | ||||||||||||||||||||||||||||||
| 7th ionization potential | 23780 kJ/mol | ||||||||||||||||||||||||||||||
| 8th ionization potential | 29287 kJ/mol | ||||||||||||||||||||||||||||||
| 9th ionization potential | 33878 kJ/mol | ||||||||||||||||||||||||||||||
| 10th ionization potential | 38726 kJ/mol | ||||||||||||||||||||||||||||||
| Most stable isotopes | |||||||||||||||||||||||||||||||
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| SI units & STP are used except where noted. | |||||||||||||||||||||||||||||||
In its crystalline form, silicon has a metallic luster and a grayish color. Even though it is a relatively inert element, silicon still reacts with halogens and dilute alkalis, but most acids (except for a combination of nitric acid and hydrofluoric acid) do not affect it. Elemental silicon transmits more than 95% of all wavelengths of infrared light.
Applications
Silicon is a very useful element that is vital to many human industries. Silicon dioxide in the form of sand and clay is an important ingredient of concrete and brick and is also used to produce Portland cement. Silicon is a very important element for plant and animal life. Diatoms extract silica from water to build their protective cell walls.
Other uses:
- Pottery/Enamel - It is a refractory material used in high-temperature material production and its silicates are used in making enamels and pottery.
- Steel - Silicon is an important constituent of some steels.
- Glass - Silica from sand is a principal component of glass. Glass can be made into a great variety of shapes and is used to make window glass, containers, and insulators, among many other uses.
- Abrasives - Silicon carbide is one of the most important abrasives.
- Semiconductor - Ultrapure silicon can be doped with arsenic, boron, gallium, or phosphorus to make silicon more conductive for use in transistors, solar cells and other semiconductor devices which are used in electronics and other high-tech applications.
- Photonics - Silicon can be used in lasers to produce coherent light with a wavelength of 456 nm.
- Medical materials - Silicones are flexible compounds containing silicon-oxygen and silicon-carbon bonds; they are widely used in applications such as artificial breast implants and contact lenses.
- LCDs and solar cells - Hydrogenated amorphous silicon has shown promise in the production of low-cost, large-area electronics in applications such as LCDs. It has also shown promise for large-area, low-cost solar cells.
- Construction - Silica is a major ingredient in bricks because of its low chemical activity.
History
Silicon (Latin silex, silicis meaning flint) was first identified by Antoine Lavoisier in 1787, and was later mistaken by Humphry Davy in 1800 for a compound. In 1811 Gay Lussac and Thenard probably prepared impure amorphous silicon through the heating of potassium with silicon tetrafluoride. In 1824 Berzelius prepared amorphous silicon using approximately the same method of Lussac. Berzelius also purified the product by repeatedly washing it.
Because silicon is an important element in semiconductor and high-tech devices, the high-tech region of Silicon Valley, California, is named after this element.
Occurrence
Silicon is a principal component of aerolites which are a class of meteoroids and also of tektites which is a natural form of glass.
Measured by weight, silicon makes up 25.7% of the earth's crust and after oxygen is also the second most abundant element. Elemental silicon is not found in nature. It occurs most often as oxides and as silicates. Sand, amethyst, agate, quartz, rock crystal, flint, jasper, and opal are some of the forms in which the oxide appears. Granite, asbestos, feldspar, clay, hornblende, and mica are a few of the many silicate minerals.
Production
Silicon is commercially prepared by the heating of high-purity silica in an electric arc furnace using carbon electrodes. At temperatures over 1900°C, the carbon reduces the silica to silicon according to the chemical equation
- SiO2 + C -->Si + CO2
Liquid silicon collects in the bottom of the furnace, and is then drained and cooled. The silicon produced via this process is called metallurgical grade silicon and is at least 99% pure. In 1997, metallurgical grade silicon cost about $ 0.50 per g.
Purification
The use of silicon in semiconductor devices demands a much greater purity than afforded by metallurgical grade silicon. Historically, a number of methods have been used to produce high-purity silicon.
Physical methodsEarly silicon purification techniques were based on the fact that if silicon is melted and re-solidified, the last parts of the mass to solidify contain most of the impurities. The earliest method of silicon purification, first described in 1919 and used on a limited basis to make radar components during World War II, involved crushing metallurgical grade silicon and then partially dissolving the silicon powder in an acid. When crushed, the silicon cracked so that the weaker impurity-rich regions were on the outside of the resulting grains of silicon. As a result, the impurity-rich silicon was the first to be dissolved when treated with acid, leaving behind a more pure product.
In zone melting, the first silicon purification method to be widely used industrially, rods of metallurgical grade silicon were heated to melt at one end. Then, the heater was slowly moved down the length of the rod, keeping a small length of the rod molten as the silicon cooled and resolidified behind it. Since most impurities tend to remain in the molten region rather than resolidify, when the process was complete, most of the impurities in the rod had been moved into end that was the last to be melted. This end was then cut off and discarded, and the process repeated if a still higher purity was desired.
Chemical methods
Today, silicon is instead purified by converting it to a silicon compound that can be more easily purified than silicon itself, and then converting that silicon compound back into pure silicon. Trichlorosilane is the silicon compound most commonly used as the intermediate, although silicon tetrachloride and silane are also used. When these gases are blown over silicon at high temperature, they decompose to high-purity silicon.
In the Siemens process, high-purity silicon rods are exposed to trichlorosilane at 1150°C. The trichlorosilane gas decomposes and deposits additional silicon onto the rods, enlarging them according to chemical reactions like
- 2 HSiCl3 -->Si + 2 HCl + SiCl4
Silicon produced from this and similar processes is called polycrystalline silicon. Polycrystalline silicon typically has impurity levels of 1 part per billion or less.
At one time, DuPont produced ultrapure silicon by reacting silicon tetrachloride with high-purity zinc vapors at 950°C, producing silicon according to the chemical equation
- SiCl4 + 2 Zn !’ Si + 2 ZnCl2
However, this technique was plagued with practical problems (such as the zinc chloride byroduct solidifying and clogging lines) and was evenutally abandoned in favor of the Siemens process.
Isotopes
Silicon has nine isotopes, with mass numbers from 25-33. Si-28 (the most abundant isotope, at 92.23%), Si-29 (4.67%), and Si-30 (3.1%) are stable; Si-32 is a radioactive isotope produced by argon decay. Its half-life, after much argument, has been determied to be approximately 276 years, and it decays by beta emission to P-32 (which has a 14.28 year half-life) and then to S-32
Precautions
A serious lung disease known as silicosis often occurred in miners, stonecutters, and others who were engaged in work where siliceous dust was inhaled in great quantities.
Reference
- Los Alamos National Laboratory – Silicon(http://periodic.lanl.gov/elements/14.html)