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"Silica" redirects here. For other uses, see Silica (disambiguation).
Silicon dioxide
Other namesSilica, Quartz, sand
Identifiers
CAS number[7631-86-9]
Properties
Molecular formulaSiO2
Molar mass60. CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 1
Appearancewhite powdery substance
solid (when pure)
Density2. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 2 g/cm³
Melting point

1650 (±75) °C

Boiling point

2230 °C

Solubility in water0. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 012 g in 100mL
Structure
Molecular shapetetrahedral
Hazards
NFPA 704
0
0
0
 
R-phrasesR42 R43 R49
S-phrasesS22 S36 S37 S45 S53
Flash pointnon-flammable
Related compounds
Other anionsSilicon sulfide
Other cationsCarbon dioxide
Germanium dioxide
Tin(IV) oxide
Lead(IV) oxide
Related compoundsSilicic acid
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

The chemical compound silicon dioxide, also known as silica or silox (from the Latin "silex"), is an oxide of silicon, chemical formula SiO2, and has been known for its hardness since the 9th century[1]. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. A tetrahedron (plural tetrahedra) is a Polyhedron composed of four triangular faces three of which meet at each vertex. Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. The flash point of a flammable liquid is the lowest Temperature at which it can form an ignitable mixture in air An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Silicon sulfide refers to the Chemical compound with the formula Si[[Sulfur S2]] An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Germanium dioxide, also called germanium oxide and germania, is an Inorganic compound, an Oxide of Germanium. Tin dioxide is the Inorganic compound with the formula SnO2 The mineral form of SnO2 is called Cassiterite, and this is the main Lead(IV oxide, PbO2 also plumbic oxide and lead dioxide, is an Oxide of Lead, with lead in Oxidation state +4 Silicic acid is a general name for a family of chemical compounds of the element Silicon, Hydrogen, and Oxygen, with the general formula n In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. in modern usage refers to a finely ground nearly pure form of Silica or Silicate. An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms. Sand is a naturally occurring Granular material composed of finely divided rock and Mineral particles Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i It is a principal component of most types of glass and substances such as concrete. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag

Contents

Manufactured forms

130m²/g surface area silica fume
130m²/g surface area silica fume

Silica is manufactured in several forms including:

It is used in the production of various products. A Desiccant is a Hygroscopic substance that induces or sustains a state of dryness ( Desiccation) in its local vicinity in a moderately-well sealed container

Health effects

Manufactured silica fume at maximum surface area of 380m²/g
Manufactured silica fume at maximum surface area of 380m²/g

Inhaling finely divided crystalline silica dust in very small quantities (OSHA allows 0. 1mg/m3) over time can lead to silicosis, bronchitis or (much more rarely) cancer, as the dust becomes lodged in the lungs and continuously irritates them, reducing lung capacities (silica does not dissolve over time). Silicosis (also known as Grinder's disease and Potter's rot) is a form of Occupational lung disease caused by inhalation of crystalline Silica Bronchitis is an Inflammation of the Bronchi. More specifically it may refer to Acute bronchitis, caused by viruses or bacteria and lasting Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled This effect can be an occupational hazard for people working with sandblasting equipment, products that contain powdered silica, and so on. Sandblasting or Bead blasting is a generic term for the process of smoothing shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds But children, asthmatics of any age, allergy sufferers and the elderly, all of whom have reduced lung capacity, can be affected in much shorter periods of time.

In all other respects, silicon dioxide is inert and harmless. When silica is ingested orally, it passes unchanged through the gastrointestinal tract, exiting in the feces, leaving no trace behind. Feces, faeces, or fæces (see spelling differences) is a waste product from an animal's digestive tract expelled through the Anus Small pieces of silicon dioxide are equally harmless, as long as they are not large enough to mechanically obstruct the GI tract, or jagged enough to lacerate its lining. Silicon dioxide produces no fumes and is insoluble in vivo. It is indigestible, with zero nutritional value and zero toxicity.

In studies across Europe (Britain/France) Amorphous Silica (aka PDMS) has been found to be biologically inert when ingested and inhaled. Warheit ET Al found during that their bio assays that any minimal damage was reversible. IN the USA the Food and Drug Administration has found it to be exempt from normal process and is allowed in food handling and processing.

Chemistry

Silicon dioxide is formed when silicon is exposed to oxygen (or air). A very thin layer (approximately 1 nm or 10 Å) of so-called 'native oxide' is formed on the surface when silicon is exposed to air under ambient conditions. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal
Higher temperatures and alternate environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures of 600 -1200 °C so-called "dry" or "wet" oxidation using O2 or H2O respectively. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the [2] The thickness of the layer of silicon replaced by the dioxide is 44% of the thickness of the silicon dioxide layer produced. [2]
Alternative methods used to deposit a layer of SiO2 include:[3]

SiH4 + 2O2 → SiO2 + 2H2O (at 400-450 °C)
Si(OC2H5)4 → SiO2 + H2O + 2C2H4
Si(OC2H5)4 + 12O2 → SiO2 + 10H2O + 8CO2

Pyrogenic silica(sometimes called fumed silica or silica fume), which is a very fine particulate form of silicon dioxide, is prepared by burning SiCl4 in an oxygen rich hydrocarbon flame to produce a "smoke" of SiO2:[4]

SiCl4 + 2H2 + O2 → SiO2 + 4HCl

Quartz exhibits a maximum solubility in water at around 340 °C [5]. Silane is a Chemical compound with Chemical formula Si[[hydrogen H]]4 Tetraethyl orthosilicate is the Chemical compound with the formula Si(OC2H54 Silicon tetrachloride is the Chemical compound with the formula SiCl4 This property is used to grow single crystals of quartz in a hydrothermal process where natural quartz is dissolved in superheated water in a pressure vessel which is cooler at the top. Crystals of 0. 5 -1 kg can be grown over a period of 1-2 months. [6] these crystals are a sourcer of very pure quartz for use in electronic applications. [4]
Fluorine reacts with silicon dioxide to form SiF4 and O2 whereas the other halogen gases (Cl2, Br2, I2) react much less readily. [4]

Silicon dioxide is attacked by hydrofluoric acid (HF) to produce "hexafluorosilicic acid":[6]

SiO2 + 6HF → H2SiF6 + 2H2O

HF is used to remove or pattern silicon dioxide in the semiconductor industry. Hydrofluoric acid is a Solution of Hydrogen fluoride in Water. Hexafluorosilicic acid is the Chemical compound with the formula H2SiF6
Silicon dioxide dissolves in hot concentrated alkali or fused hydroxide (e. g):[4]

SiO2 + NaOH → Na2SiO3 + H2O

Silicon dioxide reacts with basic metal oxides (e. E550 redirects here For the Italian locomotive see FS Class E550 Sodium silicate, also known as water glass or liquid glass, available g. sodium oxide, potassium oxide, lead(II) oxide, zinc oxide or mixtures of oxides forming silicates and glasses as the Si-O-Si bonds in silica are broken successively. Sodium oxide is a Chemical compound with the formula Na 2 O. It is used in Ceramics and Glasses Treatment with water Potassium oxide is a compound of Potassium and Oxygen. This pale yellow solid the simplest oxide of potassium is a rarely encountered highly reactive Lead(II oxide is the Chemical compound with the formula Zinc oxide is a Chemical compound with the formula ZnO It is nearly insoluble in water but soluble in Acids and Bases It occurs For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI [6] As an example the reaction of sodium oxide and SiO2 can produce sodium orthosilicate, sodium silicate and glasses, depending on the proportions of reactants:[4]

2Na2O + SiO2 → Na4SiO4
Na2O + SiO2 → Na2SiO3
(0. Sodium oxide is a Chemical compound with the formula Na 2 O. It is used in Ceramics and Glasses Treatment with water E550 redirects here For the Italian locomotive see FS Class E550 Sodium silicate, also known as water glass or liquid glass, available 25 - 0. 8)Na2O + SiO2 → glasses

Examples of such glasses have commercial significance e. g. soda lime glass,borosilicate glass, lead glass. Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type of Glass, used for windowpanes and glass containers (bottles and jars Borosilicate glass is a type of Glass with the main glass-forming constituents Silica and Boron oxide. Glass consists of a network former typically Silica (SiO2 and network modifiers including alkali fluxes such as Potassium oxide or Sodium In these glasses silica is termed the network former or lattice former. [6]
With silicon at high temperatures gaseous SiO is produced:[6]

SiO2 + Si → 2SiO (gas)

Structure and properties

SiO2 has a number of distinct crystalline forms in addition to amorphous forms. Silicon monoxide is the chemical compound with the formula SiO With the exception of stishovite and fibrous sulfur, all of the crystalline forms involve tetrahedral SiO4 units linked together by shared vertices in different arrangements. Stishovite (after SM Stishov 20th-century Russian mineralogist is an extremely hard dense Tetragonal form ( polymorph) of Silicon dioxide. Silicon-oxygen bond lengths vary between the different crystal forms, for example in α-quartz the bond length is 161 pm, whereas in α-tridymite it is in the range 154-171 pm. [6]. The Si-O-Si angle also varies between a low value of 140° in α-tridymite, up to 180° in β-tridymite. In α-quartz the Si-O-Si angle is 144°.
Fibrous sulfur has a structure similar to that of SiS2 with chains of edge-sharing SiO4 tetrahedra.
Stishovite, the highest pressure form, in contrast has a rutile like structure where silicon is 6 coordinate. Stishovite (after SM Stishov 20th-century Russian mineralogist is an extremely hard dense Tetragonal form ( polymorph) of Silicon dioxide. Titanium dioxide, also known as titanium(IV oxide or titania, is the naturally occurring Oxide of Titanium, chemical formula Ti[[oxygen The density of stishovite is 4. Stishovite (after SM Stishov 20th-century Russian mineralogist is an extremely hard dense Tetragonal form ( polymorph) of Silicon dioxide. 287 g/cm3, which compares to α-quartz, the densest of the low pressure forms, which has a density of 2. 648 g/cm3. [4] The difference in density can be ascribed to the increase in coordination as the six shortest Si-O bond lengths in stishovite (four Si-O bond lengths of 176 pm and two others of 181 pm) are greater than the Si-O bond length (161 pm) in α-quartz. [7] The change in the coordination increases the ionicity of the Si-O bond. [8]
Note that the only stable form under normal conditions is α-quartz and this is the form in which crystalline silicon dioxide is usually encountered. [4] In nature impurities in crystalline α-quartz can give rise to colours[4] (see quartz for a list). Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in

Crystalline forms of SiO2[6]
FormSpace groupStructural featuresNotes
α-quartzrhombohedral
(trigonal)		Helical chains making individual single crystals optically activeα-quartz converts to β-quartz at 573°C
β-quartzhexagonalclosely related to α-quartz (with an Si-O-Si angle of 155°) and optically activeβ-quartz converts to β-tridymite at 870°C
α-tridymiteorthorhombicmetastable form under normal pressure
β-tridymitehexagonalclosely related to α-tridymiteβ-tridymite converts to β-cristobalite 1470°C
α-cristobalitetetragonalmetastable form under normal pressure
β-cristobalitecubicclosely related to α-cristobalitemelts at 1705°C
keatitetetragonalSi5O10, Si4O14, Si8O16 ringssynthesised from amorphous silica and alkali at high pressure
coesitemonoclinicSi4O8 and Si8O16 ringshigh pressure form (higher than keatite)
stishovitetetragonalrutile like with 6 coordinate Sihigh pressure form (higher than coesite) and the densest of the polymorphs
melanophlogitecubicSi5O10, Si6O12 ringsmineral always found with hydrocarbons in interstitial spaces-a clathrasil[9]
fibrousorthorhombiclike SiS2 consisting of edge sharing chains

Molecular forms of silicon dioxide

When molecular silicon monoxide, SiO is condensed in an argon matrix cooled with helium along with oxygen atoms generated by microwave discharge molecular SiO2 is produced which has a linear structure. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in In Crystallography, the rhombohedral (or trigonal) Crystal system is one of the seven lattice point groups named after the two-dimensional Tridymite is a high-temperature polymorph of Quartz and usually occurs as minute tabular white or colorless pseudo-hexagonal Triclinic crystals or scales In Crystallography, the orthorhombic Crystal system is one of the seven Lattice Point groups Orthorhombic lattices result from stretching Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees The mineral cristobalite is a high-temperature polymorph of Quartz and Tridymite. In Crystallography, the tetragonal Crystal system is one of the 7 lattice Point groups Tetragonal Crystal lattices result from stretching a cubic In Crystallography, the tetragonal Crystal system is one of the 7 lattice Point groups Tetragonal Crystal lattices result from stretching a cubic Coesite is a form ( polymorph) of Silicon dioxide Si[[oxygen O]]2 that is formed when very high pressure (2&ndash3 Gigapascals and In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. Stishovite (after SM Stishov 20th-century Russian mineralogist is an extremely hard dense Tetragonal form ( polymorph) of Silicon dioxide. In Crystallography, the tetragonal Crystal system is one of the 7 lattice Point groups Tetragonal Crystal lattices result from stretching a cubic In Crystallography, the orthorhombic Crystal system is one of the seven Lattice Point groups Orthorhombic lattices result from stretching Silicon sulfide refers to the Chemical compound with the formula Si[[Sulfur S2]] Silicon monoxide is the chemical compound with the formula SiO [10] The Si-O bond length is 148. 3 pm which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621. 7 kJ/mol. [10]
Dimeric silicon dioxide, (SiO2)2 has been prepared by reacting O2 with matrix isolated dimeric silicon monoxide, (Si2O2). Silicon monoxide is the chemical compound with the formula SiO [10] In dimeric silicon dioxide there are two oxygen atoms bridging between the silicon atoms with an Si-O-Si angle of 94° and bond length of 164. 6 pm and the terminal Si-O bond length is 148. 2pm. [10]

Notes

  1. ^ Lynn Townsend White, Jr. (Spring, 1961). Lynn Townsend White Jr ( April 29 1907 – March 30 1987) was a professor of medieval History at Princeton, "Eilmer of Malmesbury, an Eleventh Century Aviator: A Case Study of Technological Innovation, Its Context and Tradition", Technology and Culture 2 (2), pp. 97-111 [100].

    "Ibn Firnas was a polymath: a physician, a rather bad poet, the first to make glass from stones (quartz?), a student of music, and inventor of some sort of metronome. Abbas Ibn Firnas (810 &ndash 887 AD) was also known as Abbas Qasim Ibn Firnas and العباس بن فرناس ( Arabic language) A polymath ( Greek polymathēs, πολυμαθής "having learned much" is a person whose knowledge is not restricted to one subject area Islamic poetry is poetry written by Muslims on the topic of Islam. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Islamic music is Muslim religious Music, as sung or played in public services or private devotions A metronome is any device that produces a regulated aural visual or tactile pulse to establish a steady Tempo in the performance of music "

  2. ^ a b Sunggyu Lee (2006) Encyclopedia of chemical processing , CRC Press, ISBN 0824755634
  3. ^ Robert Doering, Yoshio Nishi (2007), Handbook of Semiconductor Manufacturing Technology, CRC Press, ISBN 1574446754
  4. ^ a b c d e f g h Greenwood, N. N. ; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.  
  5. ^ The solubility of amorphous silica in water at high temperatures and high pressures Fournier R. O , Rowe J. J. , American Mineralogist (1977), 62, 1052-1056
  6. ^ a b c d e f g Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  7. ^ Wells A. F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  8. ^ Electron-density distribution in stishovite, SiO2: a new high-energy synchrotron-radiation study Kirfel A. , Krane H. -G. , Blaha P. , Schwarz K. , Lippmann T. , Acta Cryst. (2001). A57, 663-677 doi:10.1107/S0108767301010698
  9. ^ Rosemarie Szostak (1998) Molecular sieves: Principles of Synthesis and Identification, Springer,ISBN 0751404802
  10. ^ a b c d Peter Jutzi, Ulrich Schubert, (2003), Silicon chemistry: from the atom to extended systems, Wiley-VCH ISBN 3527306471

References

See also

External links

Amorphous carbonia, also called a-carbonia or a-CO2, is an exotic amorphous solid form of Carbon dioxide that is analogous to amorphous Fused quartz and fused silica are types of Glass containing primarily Silica in amorphous (non- Crystalline form Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral Mesoporous silica is a recent development in Nanotechnology. The most common types of mesoporous nanoparticles are MCM-41 and SBA-15

Dictionary

silicon dioxide

-noun

  1. (chemistry) A hard glassy mineral, SiO₂, occurring as quartz, sand, opal etc. Informally known as silica.
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