Type: Trace Element
Periodic Element: (Si)
RDA: None Listed
Importance- To Body:
There is some evidence that silicon is important to nail, hair, bone and skin health in humans.
Distribution- In Body:
* Approx. % of Body Mass
Silicon is needed for synthesis of elastin and collagen, of which the aorta contains the greatest quantity in the human body.
Excess Effects:
The Occupational Safety and Health Administration (OSHA) and The National Institute for Occupational Safety and Health (NIOSH) has set the legal limit (Permissible exposure limit) for silicon exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. Inhalation of crystalline silica dust may lead to silicosis, an occupational lung disease marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. People can be exposed to elemental silicon in the workplace by breathing it in, swallowing it, skin contact, and eye contact. In the latter two cases, silicon poses a slight hazard as an irritant.
Deficiency Effects:
Premenopausal women with higher dietary silicon intake have higher bone density, and that silicon supplementation can increase bone volume and density in patients with osteoporosis.
Sources Food:
Abundant
Sources Environmental/Geographic:
Silicon makes up 27.2% of the Earth’s crust by weight, second only to oxygen at 45.5%.
Supplemental information:
In the universe, silicon is the seventh most abundant element, coming after hydrogen, helium, carbon, nitrogen, oxygen, and neon. These abundances are not replicated well on Earth due to substantial separation of the elements taking place during the formation of the Solar System.
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| General properties | |||||||||||||||||||||||||||||||
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| Pronunciation | /ˈsɪlɪkən/ |
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| Appearance | crystalline, reflective with bluish-tinged faces | ||||||||||||||||||||||||||||||
| Standard atomic weight (Ar, standard) | [28.084, 28.086] conventional: 28.085 | ||||||||||||||||||||||||||||||
| Silicon in the periodic table | |||||||||||||||||||||||||||||||
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| Atomic number (Z) | 14 | ||||||||||||||||||||||||||||||
| Group | group 14 (carbon group) | ||||||||||||||||||||||||||||||
| Period | period 3 | ||||||||||||||||||||||||||||||
| Element category | metalloid | ||||||||||||||||||||||||||||||
| Block | p-block | ||||||||||||||||||||||||||||||
| Electron configuration | [Ne] 3s2 3p2 | ||||||||||||||||||||||||||||||
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Electrons per shell
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2, 8, 4 | ||||||||||||||||||||||||||||||
| Physical properties | |||||||||||||||||||||||||||||||
| Phase at STP | solid | ||||||||||||||||||||||||||||||
| Melting point | 1687 K (1414 °C, 2577 °F) | ||||||||||||||||||||||||||||||
| Boiling point | 3538 K (3265 °C, 5909 °F) | ||||||||||||||||||||||||||||||
| Density (near r.t.) | 2.3290 g/cm3 | ||||||||||||||||||||||||||||||
| when liquid (at m.p.) | 2.57 g/cm3 | ||||||||||||||||||||||||||||||
| Heat of fusion | 50.21 kJ/mol | ||||||||||||||||||||||||||||||
| Heat of vaporization | 383 kJ/mol | ||||||||||||||||||||||||||||||
| Molar heat capacity | 19.789 J/(mol·K) | ||||||||||||||||||||||||||||||
Vapor pressure
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| Atomic properties | |||||||||||||||||||||||||||||||
| Oxidation states | 4, 3, 2, 1 −1, −2, −3, −4 |
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| Electronegativity | Pauling scale: 1.90 | ||||||||||||||||||||||||||||||
| Ionization energies |
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| Atomic radius | empirical: 111 pm | ||||||||||||||||||||||||||||||
| Covalent radius | 111 pm | ||||||||||||||||||||||||||||||
| Van der Waals radius | 210 pm | ||||||||||||||||||||||||||||||
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| Miscellanea | |||||||||||||||||||||||||||||||
| Crystal structure | face-centered diamond-cubic
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| Speed of sound thin rod | 8433 m/s (at 20 °C) | ||||||||||||||||||||||||||||||
| Thermal expansion | 2.6 µm/(m·K) (at 25 °C) | ||||||||||||||||||||||||||||||
| Thermal conductivity | 149 W/(m·K) | ||||||||||||||||||||||||||||||
| Electrical resistivity | 2.3×103 Ω·m (at 20 °C) | ||||||||||||||||||||||||||||||
| Band gap | 1.12 eV (at 300 K) | ||||||||||||||||||||||||||||||
| Magnetic ordering | diamagnetic | ||||||||||||||||||||||||||||||
| Magnetic susceptibility | −3.9·10−6 cm3/mol (298 K) | ||||||||||||||||||||||||||||||
| Young's modulus | 130–188 GPa | ||||||||||||||||||||||||||||||
| Shear modulus | 51–80 GPa | ||||||||||||||||||||||||||||||
| Bulk modulus | 97.6 GPa | ||||||||||||||||||||||||||||||
| Poisson ratio | 0.064–0.28 | ||||||||||||||||||||||||||||||
| Mohs hardness | 6.5 | ||||||||||||||||||||||||||||||
| CAS Number | 7440-21-3 | ||||||||||||||||||||||||||||||
| History | |||||||||||||||||||||||||||||||
| Naming | after Latin 'silex' or 'silicis', meaning flint | ||||||||||||||||||||||||||||||
| Prediction | Antoine Lavoisier (1787) | ||||||||||||||||||||||||||||||
| Discovery and first isolation | Jöns Jacob Berzelius (1823) | ||||||||||||||||||||||||||||||
| Named by | Thomas Thomson (1817) | ||||||||||||||||||||||||||||||
| Main isotopes of silicon | |||||||||||||||||||||||||||||||
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Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a blue-grey metallic lustre, it is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table, along with carbon above it and germanium, tin, and lead below. It is rather unreactive, though less so than germanium, and has a very large chemical affinity for oxygen; as such, it was first prepared and characterized in pure form only in 1823 by Jöns Jakob Berzelius. Its melting and boiling points of 1414 °C and 3265 °C respectively are the second-highest among all the metalloids and nonmetals, being only surpassed by boron (carbon sublimes rather than melts at atmospheric pressure, albeit at a higher temperature than boron).
Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. It is most widely distributed in dusts, sands, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. Over 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.
Most silicon is used commercially without being separated, and often with little processing of the natural minerals. Such use includes industrial construction with clays, silica sand, and stone. Silicates are used in Portland cement for mortar and stucco, and mixed with silica sand and gravel to make concrete for walkways, foundations, and roads. They are also used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass and many other specialty glasses. Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics.
Elemental silicon also has a large impact on the modern world economy. Most free silicon is used in the steel refining, aluminium-casting, and fine chemical industries (often to make fumed silica). Even more visibly, the relatively small portion of very highly purified silicon used in semiconductor electronics (< 10%) is essential to integrated circuits — most computers, cell phones, and modern technology depend on it. Silicon is the basis of the widely used synthetic polymers called silicones.
Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, secrete skeletal structures made of silica. Silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa, horsetails and many grasses.