151-411: Silicon is a chemical element ; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor . It is a member of group 14 in the periodic table: carbon is above it; and germanium , tin , lead , and flerovium are below it. It is relatively unreactive. Silicon is a significant element that
302-501: A calque of the Latin root (e.g. Russian кремний , from кремень "flint"; Greek πυρίτιο from πυρ "fire"; Finnish pii from piikivi "flint", Czech křemík from křemen "quartz", "flint"). Gay-Lussac and Thénard are thought to have prepared impure amorphous silicon in 1811, through the heating of recently isolated potassium metal with silicon tetrafluoride , but they did not purify and characterize
453-614: A field-effect amplifier made from germanium and silicon, but he failed to build a working device, before eventually working with germanium instead. The first working transistor was a point-contact transistor built by John Bardeen and Walter Brattain later that year while working under Shockley. In 1954, physical chemist Morris Tanenbaum fabricated the first silicon junction transistor at Bell Labs . In 1955, Carl Frosch and Lincoln Derick at Bell Labs accidentally discovered that silicon dioxide ( SiO 2 ) could be grown on silicon. By 1957 Frosch and Derick published their work on
604-424: A hexagonal close-packed allotrope at about 40 gigapascals known as Si–VII (the standard modification being Si–I). An allotrope called BC8 (or bc8), having a body-centred cubic lattice with eight atoms per primitive unit cell ( space group 206 ), can be created at high pressure and remains metastable at low pressure. Its properties have been studied in detail. Silicon boils at 3265 °C: this, while high,
755-738: A pure element . In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons . Nuclear scientists, however, define a pure element as one that consists of only one isotope. For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each. However it is not isotopically pure since ordinary copper consists of two stable isotopes, 69% Cu and 31% Cu, with different numbers of neutrons. However, pure gold would be both chemically and isotopically pure, since ordinary gold consists only of one isotope, Au. Atoms of chemically pure elements may bond to each other chemically in more than one way, allowing
906-410: A common Fermi level; electrons flow from n to p, while holes flow from p to n, creating a voltage drop. This p–n junction thus acts as a diode that can rectify alternating current that allows current to pass more easily one way than the other. A transistor is an n–p–n junction, with a thin layer of weakly p-type silicon between two n-type regions. Biasing the emitter through a small forward voltage and
1057-476: A conductivity (i.e., too high a resistivity ) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, which greatly increase its conductivity and adjust its electrical response by controlling the number and charge ( positive or negative ) of activated carriers. Such control is necessary for transistors , solar cells , semiconductor detectors , and other semiconductor devices used in
1208-549: A considerable amount of time. (See element naming controversy ). Precursors of such controversies involved the nationalistic namings of elements in the late 19th century. For example, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rights to the French, often calling it cassiopeium . Similarly, the British discoverer of niobium originally named it columbium , in reference to
1359-477: A different element in nuclear reactions , which change an atom's atomic number. Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity. There was some controversy in the 1920s over whether isotopes deserved to be recognized as separate elements if they could be separated by chemical means. The term "(chemical) element"
1510-407: A disk of dust and gas orbiting the newly formed Sun. It formed via accretion, where planetesimals and other smaller rocky bodies collided and stuck, gradually growing into a planet. This process generated an enormous amount of heat, which caused early Earth to melt completely. As planetary accretion slowed, Earth began to cool, forming its first crust, called a primary or primordial crust. This crust
1661-399: A ferrosilicon alloy, and only approximately 20% is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). An estimated 15% of the world production of metallurgical grade silicon is further refined to semiconductor purity. This typically is the "nine-9" or 99.9999999% purity, nearly defect-free single crystalline material. Monocrystalline silicon of such purity
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#17327730364521812-652: A few decay products, to have been differentiated from other elements. Most recently, the synthesis of element 118 (since named oganesson ) was reported in October 2006, and the synthesis of element 117 ( tennessine ) was reported in April 2010. Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium , atomic number 43; promethium , number 61; astatine , number 85; francium , number 87; neptunium , number 93; and plutonium , number 94. These 94 elements have been detected in
1963-529: A few elements, such as silver and gold , are found uncombined as relatively pure native element minerals . Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is mostly a mixture of molecular nitrogen and oxygen , though it does contain compounds including carbon dioxide and water , as well as atomic argon , a noble gas which is chemically inert and therefore does not undergo chemical reactions. The history of
2114-450: A few nanometers to a few microns, displaying size dependent luminescent properties. The nanocrystals display large Stokes shifts converting photons in the ultraviolet range to photons in the visible or infrared, depending on the particle size, allowing for applications in quantum dot displays and luminescent solar concentrators due to their limited self absorption. A benefit of using silicon based quantum dots over cadmium or indium
2265-500: A pressure of 1 bar and a given temperature (typically at 298.15K). However, for phosphorus, the reference state is white phosphorus even though it is not the most stable allotrope, and the reference state for carbon is graphite, because the structure of graphite is more stable than that of the other allotropes. In thermochemistry , an element is defined to have an enthalpy of formation of zero in its reference state. Several kinds of descriptive categorizations can be applied broadly to
2416-483: A pressure of one atmosphere, are commonly used in characterizing the various elements. While known for most elements, either or both of these measurements is still undetermined for some of the radioactive elements available in only tiny quantities. Since helium remains a liquid even at absolute zero at atmospheric pressure, it has only a boiling point, and not a melting point, in conventional presentations. The density at selected standard temperature and pressure (STP)
2567-399: A purely notional figure given the lack of a simple Si cation in reality. At standard temperature and pressure, silicon is a shiny semiconductor with a bluish-grey metallic lustre; as typical for semiconductors, its resistivity drops as temperature rises. This arises because silicon has a small energy gap ( band gap ) between its highest occupied energy levels (the valence band) and
2718-456: A small group, (the metalloids ), having intermediate properties and often behaving as semiconductors . A more refined classification is often shown in colored presentations of the periodic table. This system restricts the terms "metal" and "nonmetal" to only certain of the more broadly defined metals and nonmetals, adding additional terms for certain sets of the more broadly viewed metals and nonmetals. The version of this classification used in
2869-453: A structural complexity unseen in oxocarbons . Silicon tends to resemble germanium far more than it does carbon, and this resemblance is enhanced by the d-block contraction , resulting in the size of the germanium atom being much closer to that of the silicon atom than periodic trends would predict. Nevertheless, there are still some differences because of the growing importance of the divalent state in germanium compared to silicon. Additionally,
3020-542: A structural material for their skeletons. Some plants accumulate silica in their tissues and require silicon for their growth, for example rice . Silicon may be taken up by plants as orthosilicic acid (also known as monosilicic acid) and transported through the xylem , where it forms amorphous complexes with components of the cell wall. This has been shown to improve cell wall strength and structural integrity in some plants, thereby reducing insect herbivory and pathogenic infections. In certain plants, silicon may also upregulate
3171-484: A trend toward increasingly complex silicate units with cooling, and the introduction of hydroxide and fluoride anions in addition to oxides. Many metals may substitute for silicon. After these igneous rocks undergo weathering , transport, and deposition, sedimentary rocks like clay, shale, and sandstone are formed. Metamorphism also may occur at high temperatures and pressures, creating an even vaster variety of minerals. There are four sources for silicon fluxes into
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#17327730364523322-474: A whole number. For example, the relative atomic mass of chlorine is 35.453 u, which differs greatly from a whole number as it is an average of about 76% chlorine-35 and 24% chlorine-37. Whenever a relative atomic mass value differs by more than ~1% from a whole number, it is due to this averaging effect, as significant amounts of more than one isotope are naturally present in a sample of that element. Chemists and nuclear scientists have different definitions of
3473-581: Is porcelain , which is based on the silicate mineral kaolinite . Traditional glass (silica-based soda–lime glass ) also functions in many of the same ways, and also is used for windows and containers. In addition, specialty silica based glass fibers are used for optical fiber , as well as to produce fiberglass for structural support and glass wool for thermal insulation . Silicones often are used in waterproofing treatments, molding compounds, mold- release agents , mechanical seals, high temperature greases and waxes, and caulking compounds. Silicone
3624-404: Is 10 (for tin , element 50). The mass number of an element, A , is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes of a given element are distinguished by their mass number, which is written as a superscript on the left hand side of the chemical symbol (e.g., U). The mass number is always an integer and has units of "nucleons". Thus, magnesium-24 (24
3775-435: Is 2.835 g/cm , with density increasing with depth from an average of 2.66 g/cm in the uppermost crust to 3.1 g/cm at the base of the crust. In contrast to the continental crust, the oceanic crust is composed predominantly of pillow lava and sheeted dikes with the composition of mid-ocean ridge basalt, with a thin upper layer of sediments and a lower layer of gabbro . Earth formed approximately 4.6 billion years ago from
3926-606: Is a mixture of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C. Most (54 of 94) naturally occurring elements have more than one stable isotope. Except for the isotopes of hydrogen (which differ greatly from each other in relative mass—enough to cause chemical effects), the isotopes of a given element are chemically nearly indistinguishable. All elements have radioactive isotopes (radioisotopes); most of these radioisotopes do not occur naturally. Radioisotopes typically decay into other elements via alpha decay , beta decay , or inverse beta decay ; some isotopes of
4077-422: Is a deep water Si gradient of greater than 0.3 parts per thousand. Si is most commonly associated with productivity in the oceans. Crystalline bulk silicon is rather inert, but becomes more reactive at high temperatures. Like its neighbour aluminium, silicon forms a thin, continuous surface layer of silicon dioxide ( SiO 2 ) that protects the metal from oxidation. Thus silicon does not measurably react with
4228-406: Is a dimensionless number equal to the atomic mass divided by the atomic mass constant , which equals 1 Da. In general, the mass number of a given nuclide differs in value slightly from its relative atomic mass, since the mass of each proton and neutron is not exactly 1 Da; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and because of
4379-430: Is a major structural motif in silicon chemistry just as it is for carbon chemistry. However, the 3p subshell is rather more diffuse than the 2p subshell and does not hybridise so well with the 3s subshell. As a result, the chemistry of silicon and its heavier congeners shows significant differences from that of carbon, and thus octahedral coordination is also significant. For example, the electronegativity of silicon (1.90)
4530-494: Is also sometimes used in breast implants , contact lenses, explosives and pyrotechnics . Silly Putty was originally made by adding boric acid to silicone oil . Other silicon compounds function as high-technology abrasives and new high-strength ceramics based upon silicon carbide . Silicon is a component of some superalloys . Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent
4681-812: Is an ongoing area of scientific study. The lightest elements are hydrogen and helium , both created by Big Bang nucleosynthesis in the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium . Almost all other elements found in nature were made by various natural methods of nucleosynthesis . On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation . New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay , beta decay , spontaneous fission , cluster decay , and other rarer modes of decay. Of
Silicon - Misplaced Pages Continue
4832-460: Is based on a Latin or other traditional word, for example adopting "gold" rather than "aurum" as the name for the 79th element (Au). IUPAC prefers the British spellings " aluminium " and "caesium" over the U.S. spellings "aluminum" and "cesium", and the U.S. "sulfur" over British "sulphur". However, elements that are practical to sell in bulk in many countries often still have locally used national names, and countries whose national language does not use
4983-427: Is conducted in the presence of scrap iron with low amounts of phosphorus and sulfur , producing ferrosilicon . Ferrosilicon, an iron-silicon alloy that contains varying ratios of elemental silicon and iron, accounts for about 80% of the world's production of elemental silicon, with China, the leading supplier of elemental silicon, providing 4.6 million tonnes (or 2/3rds of world output) of silicon, most of it in
5134-401: Is deposited in many plant tissues. Owing to the abundance of silicon in the Earth's crust , natural silicon-based materials have been used for thousands of years. Silicon rock crystals were familiar to various ancient civilizations , such as the predynastic Egyptians who used it for beads and small vases , as well as the ancient Chinese . Glass containing silica was manufactured by
5285-483: Is deposited into the world's oceans each year. Of that value, 80–240 megatonnes are in the form of particulate silicon. The total amount of particulate silicon deposition into the ocean is still less than the amount of silicon influx into the ocean via riverine transportation. Aeolian inputs of particulate lithogenic silicon into the North Atlantic and Western North Pacific oceans are the result of dust settling on
5436-401: Is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle. The most incompatible elements are enriched by a factor of 50 to 100 in the continental crust relative to primitive mantle rock, while oceanic crust is enriched with incompatible elements by a factor of about 10. The estimated average density of the continental crust
5587-502: Is essential for several physiological and metabolic processes in plants. Silicon is widely regarded as the predominant semiconductor material due to its versatile applications in various electrical devices such as transistors, solar cells, integrated circuits, and others. These may be due to its significant band gap, expansive optical transmission range, extensive absorption spectrum, surface roughening, and effective anti-reflection coating. Because of its high chemical affinity for oxygen, it
5738-533: Is essential to the transistors and integrated circuit chips used in most modern technology such as smartphones and other computers . In 2019, 32.4% of the semiconductor market segment was for networks and communications devices, and the semiconductors industry is projected to reach $ 726.73 billion by 2027. Silicon is an essential element in biology. Only traces are required by most animals, but some sea sponges and microorganisms, such as diatoms and radiolaria , secrete skeletal structures made of silica. Silica
5889-432: Is highly exothermic and hence requires no outside energy source. Hyperfine silicon is made at a higher purity than almost any other material: transistor production requires impurity levels in silicon crystals less than 1 part per 10, and in special cases impurity levels below 1 part per 10 are needed and attained. Silicon nanostructures can directly be produced from silica sand using conventional metalothermic processes, or
6040-407: Is its thick outer shell of rock , referring to less than one percent of the planet's radius and volume . It is the top component of the lithosphere , a solidified division of Earth 's layers that includes the crust and the upper part of the mantle . The lithosphere is broken into tectonic plates whose motion allows heat to escape the interior of Earth into space. The crust lies on top of
6191-432: Is largely composed of carbon , but astrobiology considers that extraterrestrial life may have other hypothetical types of biochemistry . Silicon is considered an alternative to carbon, as it can create complex and stable molecules with four covalent bonds, required for a DNA -analog, and it is available in large quantities. Chemical element A chemical element is a chemical substance whose atoms all have
Silicon - Misplaced Pages Continue
6342-470: Is much less than that of carbon (2.55), because the valence electrons of silicon are further from the nucleus than those of carbon and hence experience smaller electrostatic forces of attraction from the nucleus. The poor overlap of 3p orbitals also results in a much lower tendency toward catenation (formation of Si–Si bonds) for silicon than for carbon, due to the concomitant weakening of the Si–Si bond compared to
6493-518: Is of use in NMR and EPR spectroscopy , as it is the only one with a nuclear spin ( I = 1 / 2 ). All three are produced in Type Ia supernovae through the oxygen-burning process , with Si being made as part of the alpha process and hence the most abundant. The fusion of Si with alpha particles by photodisintegration rearrangement in stars is known as the silicon-burning process ; it
6644-436: Is often used in characterizing the elements. Density is often expressed in grams per cubic centimetre (g/cm ). Since several elements are gases at commonly encountered temperatures, their densities are usually stated for their gaseous forms; when liquefied or solidified, the gaseous elements have densities similar to those of the other elements. When an element has allotropes with different densities, one representative allotrope
6795-499: Is still lower than the temperature at which its lighter congener carbon sublimes (3642 °C) and silicon similarly has a lower heat of vaporisation than carbon, consistent with the fact that the Si–Si bond is weaker than the C–C bond. It is also possible to construct silicene layers analogous to graphene . Naturally occurring silicon is composed of three stable isotopes , Si (92.23%), Si (4.67%), and Si (3.10%). Out of these, only Si
6946-518: Is the basis of the widely used synthetic polymers called silicones . The late 20th century to early 21st century has been described as the Silicon Age (also known as the Digital Age or Information Age ) because of the large impact that elemental silicon has on the modern world economy. The small portion of very highly purified elemental silicon used in semiconductor electronics (<15%)
7097-407: Is the last stage of stellar nucleosynthesis before the rapid collapse and violent explosion of the star in question in a type II supernova . Twenty-two radioisotopes have been characterized, the two stablest being Si with a half-life of about 150 years, and Si with a half-life of 2.62 hours. All the remaining radioactive isotopes have half-lives that are less than seven seconds, and
7248-426: Is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons). Whereas the mass number simply counts the total number of neutrons and protons and is thus an integer, the atomic mass of a particular isotope (or "nuclide") of the element is the mass of a single atom of that isotope, and is typically expressed in daltons (symbol: Da), or universal atomic mass units (symbol: u). Its relative atomic mass
7399-504: Is the non-toxic, metal-free nature of silicon. Another application of silicon quantum dots is for sensing of hazardous materials. The sensors take advantage of the luminescent properties of the quantum dots through quenching of the photoluminescence in the presence of the hazardous substance. There are many methods used for hazardous chemical sensing with a few being electron transfer, fluorescence resonance energy transfer , and photocurrent generation. Electron transfer quenching occurs when
7550-532: Is typically selected in summary presentations, while densities for each allotrope can be stated where more detail is provided. For example, the three familiar allotropes of carbon ( amorphous carbon , graphite , and diamond ) have densities of 1.8–2.1, 2.267, and 3.515 g/cm , respectively. The elements studied to date as solid samples have eight kinds of crystal structures : cubic , body-centered cubic , face-centered cubic, hexagonal , monoclinic , orthorhombic , rhombohedral , and tetragonal . For some of
7701-531: Is used in building mortar and modern stucco , but more importantly, combined with silica sand, and gravel (usually containing silicate minerals such as granite), to make the concrete that is the basis of most of the very largest industrial building projects of the modern world. Silica is used to make fire brick , a type of ceramic. Silicate minerals are also in whiteware ceramics , an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example
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#17327730364527852-486: Is used in the chemical industry. However, even greater purity is needed for semiconductor applications, and this is produced from the reduction of tetrachlorosilane (silicon tetrachloride) or trichlorosilane . The former is made by chlorinating scrap silicon and the latter is a byproduct of silicone production. These compounds are volatile and hence can be purified by repeated fractional distillation , followed by reduction to elemental silicon with very pure zinc metal as
8003-417: Is used in two different but closely related meanings: it can mean a chemical substance consisting of a single kind of atoms, or it can mean that kind of atoms as a component of various chemical substances. For example, molecules of water (H 2 O) contain atoms of hydrogen (H) and oxygen (O), so water can be said as a compound consisting of the elements hydrogen (H) and oxygen (O) even though it does not contain
8154-520: Is usually produced by the Czochralski process , and is used to produce silicon wafers used in the semiconductor industry , in electronics, and in some high-cost and high-efficiency photovoltaic applications. Pure silicon is an intrinsic semiconductor , which means that unlike metals, it conducts electron holes and electrons released from atoms by heat; silicon's electrical conductivity increases with higher temperatures. Pure silicon has too low
8305-429: Is very strong; fullerenes , which have nearly spherical shapes; and carbon nanotubes , which are tubes with a hexagonal structure (even these may differ from each other in electrical properties). The ability of an element to exist in one of many structural forms is known as 'allotropy'. The reference state of an element is defined by convention, usually as the thermodynamically most stable allotrope and physical state at
8456-590: Is widely used. For example, the French chemical terminology distinguishes élément chimique (kind of atoms) and corps simple (chemical substance consisting of a single kind of atoms); the Russian chemical terminology distinguishes химический элемент and простое вещество . Almost all baryonic matter in the universe is composed of elements (among rare exceptions are neutron stars ). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds . Only
8607-760: The Canadian Shield , and on other cratonic regions such as those on the Fennoscandian Shield . Some zircon with age as great as 4.3 billion years has been found in the Narryer Gneiss Terrane . Continental crust is a tertiary crust, formed at subduction zones through recycling of subducted secondary (oceanic) crust. The average age of Earth's current continental crust has been estimated to be about 2.0 billion years. Most crustal rocks formed before 2.5 billion years ago are located in cratons . Such an old continental crust and
8758-465: The Egyptians since at least 1500 BC, as well as by the ancient Phoenicians . Natural silicate compounds were also used in various types of mortar for construction of early human dwellings . In 1787, Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element , but the chemical affinity of silicon for oxygen is high enough that he had no means to reduce
8909-489: The International Union of Pure and Applied Chemistry (IUPAC) had recognized a total of 118 elements. The first 94 occur naturally on Earth , and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements (radioelements) which decay quickly, nearly all elements are available industrially in varying amounts. The discovery and synthesis of further new elements
9060-638: The Latin alphabet are likely to use the IUPAC element names. According to IUPAC, element names are not proper nouns; therefore, the full name of an element is not capitalized in English, even if derived from a proper noun , as in californium and einsteinium . Isotope names are also uncapitalized if written out, e.g., carbon-12 or uranium-235 . Chemical element symbols (such as Cf for californium and Es for einsteinium), are always capitalized (see below). In
9211-602: The New World . It was used extensively as such by American publications before the international standardization (in 1950). Before chemistry became a science , alchemists designed arcane symbols for both metals and common compounds. These were however used as abbreviations in diagrams or procedures; there was no concept of atoms combining to form molecules . With his advances in the atomic theory of matter, John Dalton devised his own simpler symbols, based on circles, to depict molecules. Earth%27s crust Earth's crust
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#17327730364529362-444: The automotive industry . Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a eutectic mixture which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium. Most elemental silicon produced remains as
9513-745: The halogens ; fluorine attacks silicon vigorously at room temperature, chlorine does so at about 300 °C, and bromine and iodine at about 500 °C. Silicon does not react with most aqueous acids, but is oxidised and complexed by hydrofluoric acid mixtures containing either chlorine or nitric acid to form hexafluorosilicates . It readily dissolves in hot aqueous alkali to form silicates . At high temperatures, silicon also reacts with alkyl halides ; this reaction may be catalysed by copper to directly synthesise organosilicon chlorides as precursors to silicone polymers. Upon melting, silicon becomes extremely reactive, alloying with most metals to form silicides , and reducing most metal oxides because
9664-483: The heat of formation of silicon dioxide is so large. In fact, molten silicon reacts virtually with every known kind of crucible material (except its own oxide, SiO 2 ). This happens due to silicon's high binding forces for the light elements and to its high dissolving power for most elements. As a result, containers for liquid silicon must be made of refractory , unreactive materials such as zirconium dioxide or group 4, 5, and 6 borides. Tetrahedral coordination
9815-423: The kinetic isotope effect is significant). Thus, all carbon isotopes have nearly identical chemical properties because they all have six electrons, even though they may have 6 to 8 neutrons. That is why atomic number, rather than mass number or atomic weight , is considered the identifying characteristic of an element. The symbol for atomic number is Z . Isotopes are atoms of the same element (that is, with
9966-418: The lowest unoccupied molecular orbital (LUMO) is slightly lower in energy than the conduction band of the quantum dot, allowing for the transfer of electrons between the two, preventing recombination of the holes and electrons within the nanocrystals. The effect can also be achieved in reverse with a donor molecule having its highest occupied molecular orbital (HOMO) slightly higher than a valence band edge of
10117-453: The mantle makes up 68.1% of the Earth's mass and is composed mostly of denser oxides and silicates, an example being olivine , (Mg,Fe) 2 SiO 4 ; while the lighter siliceous minerals such as aluminosilicates rise to the surface and form the crust, making up 0.4% of the Earth's mass. The crystallisation of igneous rocks from magma depends on a number of factors; among them are
10268-405: The nuclear binding energy and electron binding energy. For example, the atomic mass of chlorine-35 to five significant digits is 34.969 Da and that of chlorine-37 is 36.966 Da. However, the relative atomic mass of each isotope is quite close to its mass number (always within 1%). The only isotope whose atomic mass is exactly a natural number is C, which has a mass of 12 Da; because
10419-408: The photocurrent emitted by the quantum dots instead of monitoring the photoluminescent display. If the concentration of the desired chemical increases then the photocurrent given off by the nanocrystals will change in response. Although silicon is readily available in the form of silicates , very few organisms use it directly. Diatoms , radiolaria , and siliceous sponges use biogenic silica as
10570-592: The 20th century saw the development of the chemistry and industrial use of siloxanes and the growing use of silicone polymers , elastomers , and resins . In the late 20th century, the complexity of the crystal chemistry of silicides was mapped, along with the solid-state physics of doped semiconductors . The first semiconductor devices did not use silicon, but used galena , including German physicist Ferdinand Braun 's crystal detector in 1874 and Indian physicist Jagadish Chandra Bose 's radio crystal detector in 1901. The first silicon semiconductor device
10721-638: The 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium , element 43 and promethium , element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of
10872-529: The C–C bond: the average Si–Si bond energy is approximately 226 kJ/mol, compared to a value of 356 kJ/mol for the C–C bond. This results in multiply bonded silicon compounds generally being much less stable than their carbon counterparts, an example of the double bond rule . On the other hand, the presence of radial nodes in the 3p orbitals of silicon suggests the possibility of hypervalence , as seen in five and six-coordinate derivatives of silicon such as SiX 5 and SiF 6 . Lastly, because of
11023-535: The Earth's crust is composed of silicate minerals , which are compounds of silicon and oxygen, often with metallic ions when negatively charged silicate anions require cations to balance the charge. Many of these have direct commercial uses, such as clays, silica sand, and most kinds of building stone. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide). Silicates are used in making Portland cement (made mostly of calcium silicates) which
11174-487: The French, Italians, Greeks, Portuguese and Poles prefer "azote/azot/azoto" (from roots meaning "no life") for "nitrogen". For purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognized are decided by the International Union of Pure and Applied Chemistry (IUPAC), which has decided on a sort of international English language, drawing on traditional English names even when an element's chemical symbol
11325-399: The air below 900 °C, but formation of the vitreous dioxide rapidly increases between 950 °C and 1160 °C and when 1400 °C is reached, atmospheric nitrogen also reacts to give the nitrides SiN and Si 3 N 4 . Silicon reacts with gaseous sulfur at 600 °C and gaseous phosphorus at 1000 °C. This oxide layer nevertheless does not prevent reaction with
11476-487: The atomic masses of the elements (their atomic weights or atomic masses) do not always increase monotonically with their atomic numbers. The naming of various substances now known as elements precedes the atomic theory of matter, as names were given locally by various cultures to various minerals, metals, compounds, alloys, mixtures, and other materials, though at the time it was not known which chemicals were elements and which compounds. As they were identified as elements,
11627-406: The behavior of its oxide compounds and its reaction with acids as well as bases (though this takes some effort), and is hence often referred to as a metalloid rather than a nonmetal. Germanium shows more, and tin is generally considered a metal. Silicon shows clear differences from carbon. For example, organic chemistry has very few analogies with silicon chemistry, while silicate minerals have
11778-480: The boundary with the underlying mantle. The temperature increases by as much as 30 °C (54 °F) for every kilometer locally in the upper part of the crust. Earth's 40-kilometre (25-mile) deep crust—just one percent of Earth’s mass —contains all known life in the Universe . The crust of Earth is of two distinct types: The average thickness of the crust is about 15 – 20 km (9 – 12 mi). Because both
11929-583: The central silicon atom shares an electron pair with each of the four atoms it is bonded to. The first four ionisation energies of silicon are 786.3, 1576.5, 3228.3, and 4354.4 kJ/mol respectively; these figures are high enough to preclude the possibility of simple cationic chemistry for the element. Following periodic trends , its single-bond covalent radius of 117.6 pm is intermediate between those of carbon (77.2 pm) and germanium (122.3 pm). The hexacoordinate ionic radius of silicon may be considered to be 40 pm, although this must be taken as
12080-418: The chemical composition of the magma, the cooling rate, and some properties of the individual minerals to be formed, such as lattice energy , melting point, and complexity of their crystal structure. As magma is cooled, olivine appears first, followed by pyroxene , amphibole , biotite mica, orthoclase feldspar , muscovite mica , quartz , zeolites , and finally, hydrothermal minerals. This sequence shows
12231-413: The chemical substances (di)hydrogen (H 2 ) and (di)oxygen (O 2 ), as H 2 O molecules are different from H 2 and O 2 molecules. For the meaning "chemical substance consisting of a single kind of atoms", the terms "elementary substance" and "simple substance" have been suggested, but they have not gained much acceptance in English chemical literature, whereas in some other languages their equivalent
12382-417: The collector through a large reverse voltage allows the transistor to act as a triode amplifier. Silicon crystallises in a giant covalent structure at standard conditions, specifically in a diamond cubic crystal lattice ( space group 227 ). It thus has a high melting point of 1414 °C, as a lot of energy is required to break the strong covalent bonds and melt the solid. Upon melting silicon contracts as
12533-409: The combustion synthesis approach. Such nanostructured silicon materials can be used in various functional applications including the anode of lithium-ion batteries (LIBs), other ion batteries, future computing devices like memristors or photocatalytic applications. Most silicon is used industrially without being purified, often with comparatively little processing from its natural form. More than 90% of
12684-502: The composition is not uniform, with the upper crust averaging a more felsic composition similar to that of dacite , while the lower crust averages a more mafic composition resembling basalt. The most abundant minerals in Earth 's continental crust are feldspars , which make up about 41% of the crust by weight, followed by quartz at 12%, and pyroxenes at 11%. All the other constituents except water occur only in very small quantities and total less than 1%. Continental crust
12835-521: The computer industry and other technical applications. In silicon photonics , silicon may be used as a continuous wave Raman laser medium to produce coherent light. In common integrated circuits , a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping and insulated from each other by thin layers of silicon oxide , an insulator that is easily produced on Si surfaces by processes of thermal oxidation or local oxidation (LOCOS) , which involve exposing
12986-410: The conduction band either thermally or photolytically, creating an n-type semiconductor . Similarly, doping silicon with a group 13 element such as boron , aluminium , or gallium results in the introduction of acceptor levels that trap electrons that may be excited from the filled valence band, creating a p-type semiconductor . Joining n-type silicon to p-type silicon creates a p–n junction with
13137-484: The continental and oceanic crust are less dense than the mantle below, both types of crust "float" on the mantle. The surface of the continental crust is significantly higher than the surface of the oceanic crust, due to the greater buoyancy of the thicker, less dense continental crust (an example of isostasy ). As a result, the continents form high ground surrounded by deep ocean basins. The continental crust has an average composition similar to that of andesite , though
13288-408: The dalton is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state. The standard atomic weight (commonly called "atomic weight") of an element is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance, relative to the atomic mass unit. This number may be a fraction that is not close to
13439-416: The discovery and use of elements began with early human societies that discovered native minerals like carbon , sulfur , copper and gold (though the modern concept of an element was not yet understood). Attempts to classify materials such as these resulted in the concepts of classical elements , alchemy , and similar theories throughout history. Much of the modern understanding of elements developed from
13590-1761: The dominant materials during their respective ages of civilization . Because silicon is an important element in high-technology semiconductor devices, many places in the world bear its name. For example, the Santa Clara Valley in California acquired the nickname Silicon Valley , as the element is the base material in the semiconductor industry there. Since then, many other places have been similarly dubbed, including Silicon Wadi in Israel; Silicon Forest in Oregon; Silicon Hills in Austin, Texas; Silicon Slopes in Salt Lake City, Utah; Silicon Saxony in Germany; Silicon Valley in India; Silicon Border in Mexicali, Mexico; Silicon Fen in Cambridge, England; Silicon Roundabout in London; Silicon Glen in Scotland; Silicon Gorge in Bristol, England; Silicon Alley in New York City; and Silicon Beach in Los Angeles. A silicon atom has fourteen electrons . In
13741-531: The element to oxygen under the proper conditions that can be predicted by the Deal–Grove model . Silicon has become the most popular material for both high power semiconductors and integrated circuits because it can withstand the highest temperatures and greatest electrical activity without suffering avalanche breakdown (an electron avalanche is created when heat produces free electrons and holes, which in turn pass more current, which produces more heat). In addition,
13892-406: The elements are available by name, atomic number, density, melting point, boiling point and chemical symbol , as well as ionization energy . The nuclides of stable and radioactive elements are also available as a list of nuclides , sorted by length of half-life for those that are unstable. One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of
14043-470: The elements are often summarized using the periodic table, which powerfully and elegantly organizes the elements by increasing atomic number into rows ( "periods" ) in which the columns ( "groups" ) share recurring ("periodic") physical and chemical properties. The table contains 118 confirmed elements as of 2021. Although earlier precursors to this presentation exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended
14194-480: The elements can be uniquely sequenced by atomic number, conventionally from lowest to highest (as in a periodic table), sets of elements are sometimes specified by such notation as "through", "beyond", or "from ... through", as in "through iron", "beyond uranium", or "from lanthanum through lutetium". The terms "light" and "heavy" are sometimes also used informally to indicate relative atomic numbers (not densities), as in "lighter than carbon" or "heavier than lead", though
14345-413: The elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic number greater than 82. Of the 80 elements with at least one stable isotope, 26 have only one stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes for a single element
14496-474: The elements, including consideration of their general physical and chemical properties, their states of matter under familiar conditions, their melting and boiling points, their densities, their crystal structures as solids, and their origins. Several terms are commonly used to characterize the general physical and chemical properties of the chemical elements. A first distinction is between metals , which readily conduct electricity , nonmetals , which do not, and
14647-493: The emitted electron carries up to 1.48 MeV of energy. The known isotopes of silicon range in mass number from 22 to 46. The most common decay mode of the isotopes with mass numbers lower than the three stable isotopes is inverse beta decay , primarily forming aluminium isotopes (13 protons) as decay products . The most common decay mode for the heavier unstable isotopes is beta decay, primarily forming phosphorus isotopes (15 protons) as decay products. Silicon can enter
14798-492: The existing names for anciently known elements (e.g., gold, mercury, iron) were kept in most countries. National differences emerged over the element names either for convenience, linguistic niceties, or nationalism. For example, German speakers use "Wasserstoff" (water substance) for "hydrogen", "Sauerstoff" (acid substance) for "oxygen" and "Stickstoff" (smothering substance) for "nitrogen"; English and some other languages use "sodium" for "natrium", and "potassium" for "kalium"; and
14949-630: The explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System . At over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope, and is almost always considered on par with the 80 stable elements. The heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized . There are now 118 known elements. In this context, "known" means observed well enough, even from just
15100-493: The first manufactured SiO 2 semiconductor oxide transistor: the first planar transistors, in which drain and source were adjacent at the same surface. The "Silicon Age" refers to the late 20th century to early 21st century. This is due to silicon being the dominant material of the Silicon Age (also known as the Digital Age or Information Age ), similar to how the Stone Age , Bronze Age and Iron Age were defined by
15251-406: The first volatile hydrides of silicon, synthesising trichlorosilane in 1857 and silane itself in 1858, but a detailed investigation of the silanes was only carried out in the early 20th century by Alfred Stock , despite early speculation on the matter dating as far back as the beginnings of synthetic organic chemistry in the 1830s. Similarly, the first organosilicon compound , tetraethylsilane,
15402-575: The form of ferrosilicon. It is followed by Russia (610,000 t), Norway (330,000 t), Brazil (240,000 t), and the United States (170,000 t). Ferrosilicon is primarily used by the iron and steel industry (see below ) with primary use as alloying addition in iron or steel and for de-oxidation of steel in integrated steel plants. Another reaction, sometimes used, is aluminothermal reduction of silicon dioxide, as follows: Leaching powdered 96–97% pure silicon with water results in ~98.5% pure silicon, which
15553-418: The formation of cementite where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of
15704-529: The formation of Earth, they are certain to have completely decayed, and if present in novae, are in quantities too small to have been noted. Technetium was the first purportedly non-naturally occurring element synthesized, in 1937, though trace amounts of technetium have since been found in nature (and also the element may have been discovered naturally in 1925). This pattern of artificial production and later natural discovery has been repeated with several other radioactive naturally occurring rare elements. List of
15855-465: The formation of the Solar System . Silicon makes up 27.2% of the Earth's crust by weight, second only to oxygen at 45.5%, with which it always is associated in nature. Further fractionation took place in the formation of the Earth by planetary differentiation : Earth's core , which makes up 31.5% of the mass of the Earth, has approximate composition Fe 25 Ni 2 Co 0.1 S 3 ;
16006-519: The ground state, they are arranged in the electron configuration [Ne]3s3p. Of these, four are valence electrons , occupying the 3s orbital and two of the 3p orbitals. Like the other members of its group, the lighter carbon and the heavier germanium , tin , and lead , it has the same number of valence electrons as valence orbitals: hence, it can complete its octet and obtain the stable noble gas configuration of argon by forming sp hybrid orbitals , forming tetrahedral SiX 4 derivatives where
16157-431: The half-lives predicted for the observationally stable lead isotopes range from 10 to 10 years. Elements with atomic numbers 43, 61, and 83 through 94 are unstable enough that their radioactive decay can be detected. Three of these elements, bismuth (element 83), thorium (90), and uranium (92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced
16308-399: The heaviest elements also undergo spontaneous fission . Isotopes that are not radioactive, are termed "stable" isotopes. All known stable isotopes occur naturally (see primordial nuclide ). The many radioisotopes that are not found in nature have been characterized after being artificially produced. Certain elements have no stable isotopes and are composed only of radioisotopes: specifically
16459-549: The heavy elements before the formation of the Solar System. For example, at over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope. The last 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus are not known to occur in nature at all. 1 The properties of
16610-430: The increasing energy gap between the valence s and p orbitals as the group is descended, the divalent state grows in importance from carbon to lead, so that a few unstable divalent compounds are known for silicon; this lowering of the main oxidation state, in tandem with increasing atomic radii, results in an increase of metallic character down the group. Silicon already shows some incipient metallic behavior, particularly in
16761-578: The insulating oxide of silicon is not soluble in water, which gives it an advantage over germanium (an element with similar properties which can also be used in semiconductor devices) in certain fabrication techniques. Monocrystalline silicon is expensive to produce, and is usually justified only in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) used in
16912-433: The lesser grade is growing more quickly than for monocrystalline silicon. By 2013, polycrystalline silicon production, used mostly in solar cells, was projected to reach 200,000 metric tons per year, while monocrystalline semiconductor grade silicon was expected to remain less than 50,000 tons per year. Silicon quantum dots are created through the thermal processing of hydrogen silsesquioxane into nanocrystals ranging from
17063-402: The long-range tetrahedral network of bonds breaks up and the voids in that network are filled in, similar to water ice when hydrogen bonds are broken upon melting. It does not have any thermodynamically stable allotropes at standard pressure, but several other crystal structures are known at higher pressures. The general trend is one of increasing coordination number with pressure, culminating in
17214-470: The lower Ge–O bond strength compared to the Si–O bond strength results in the absence of "germanone" polymers that would be analogous to silicone polymers. Silicon is the eighth most abundant element in the universe, coming after hydrogen , helium , carbon , nitrogen , oxygen , iron , and neon . These abundances are not replicated well on Earth due to substantial separation of the elements taking place during
17365-449: The lowest unoccupied ones (the conduction band). The Fermi level is about halfway between the valence and conduction bands and is the energy at which a state is as likely to be occupied by an electron as not. Hence pure silicon is effectively an insulator at room temperature. However, doping silicon with a pnictogen such as phosphorus , arsenic , or antimony introduces one extra electron per dopant and these may then be excited into
17516-432: The majority of these have half-lives that are less than one-tenth of a second. Silicon has one known nuclear isomer , Si, with a half-life less than 210 nanoseconds. Si undergoes low-energy beta decay to P and then stable S . Si may be produced by the neutron activation of natural silicon and is thus useful for quantitative analysis; it can be easily detected by its characteristic beta decay to stable P , in which
17667-520: The mantle, a configuration that is stable because the upper mantle is made of peridotite and is therefore significantly denser than the crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity , a boundary defined by a contrast in seismic velocity. The temperature of the crust increases with depth, reaching values typically in the range from about 100 °C (212 °F) to 600 °C (1,112 °F) at
17818-594: 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 silicate -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. Silicon
17969-421: The ocean: chemical weathering of continental rocks, river transport, dissolution of continental terrigenous silicates, and the reaction between submarine basalts and hydrothermal fluid which release dissolved silicon. All four of these fluxes are interconnected in the ocean's biogeochemical cycle as they all were initially formed from the weathering of Earth's crust. Approximately 300–900 megatonnes of Aeolian dust
18120-638: The oceans from the Sahara and Gobi Desert, respectively. Riverine transports are the major source of silicon influx into the ocean in coastal regions, while silicon deposition in the open ocean is greatly influenced by the settling of Aeolian dust. Silicon of 96–99% purity is made by carbothermically reducing quartzite or sand with highly pure coke . The reduction is carried out in an electric arc furnace , with an excess of SiO 2 used to stop silicon carbide (SiC) from accumulating: This reaction, known as carbothermal reduction of silicon dioxide, usually
18271-489: The oceans through groundwater and riverine transport. Large fluxes of groundwater input have an isotopic composition which is distinct from riverine silicon inputs. Isotopic variations in groundwater and riverine transports contribute to variations in oceanic Si values. Currently, there are substantial differences in the isotopic values of deep water in the world's ocean basins . Between the Atlantic and Pacific oceans, there
18422-618: The old ocean crust means that the oldest ocean crust on Earth today is only about 200 million years old. In contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4.28 billion years and have been found in the Narryer Gneiss Terrane in Western Australia , in the Acasta Gneiss in the Northwest Territories on
18573-503: The oxide and isolate the element. After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin silex , silicis for flint, and adding the "-ium" ending because he believed it to be a metal. Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology (e.g. German Silizium , Turkish silisyum , Catalan silici , Armenian Սիլիցիում or Silitzioum ). A few others use instead
18724-418: The periodic table, which groups together elements with similar chemical properties (and usually also similar electronic structures). The atomic number of an element is equal to the number of protons in each atom, and defines the element. For example, all carbon atoms contain 6 protons in their atomic nucleus ; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of
18875-426: The periodic tables presented here includes: actinides , alkali metals , alkaline earth metals , halogens , lanthanides , transition metals , post-transition metals , metalloids , reactive nonmetals , and noble gases . In this system, the alkali metals, alkaline earth metals, and transition metals, as well as the lanthanides and the actinides, are special groups of the metals viewed in a broader sense. Similarly,
19026-569: The product to a brown powder by repeatedly washing it. As a result, he is usually given credit for the element's discovery. The same year, Berzelius became the first to prepare silicon tetrachloride ; silicon tetrafluoride had already been prepared long before in 1771 by Carl Wilhelm Scheele by dissolving silica in hydrofluoric acid . In 1823 for the first time Jacob Berzelius discovered silicon tetrachloride (SiCl 4 ). In 1846 Von Ebelman's synthesized tetraethyl orthosilicate (Si(OC 2 H 5 ) 4 ). Silicon in its more common crystalline form
19177-448: The product, nor identify it as a new element. Silicon was given its present name in 1817 by Scottish chemist Thomas Thomson . He retained part of Davy's name but added "-on" because he believed that silicon was a nonmetal similar to boron and carbon . In 1824, Jöns Jacob Berzelius prepared amorphous silicon using approximately the same method as Gay-Lussac (reducing potassium fluorosilicate with molten potassium metal), but purifying
19328-400: The production of low-cost, large-area electronics in applications such as liquid crystal displays and of large-area, low-cost, thin-film solar cells . Such semiconductor grades of silicon are either slightly less pure or polycrystalline rather than monocrystalline, and are produced in comparable quantities as the monocrystalline silicon: 75,000 to 150,000 metric tons per year. The market for
19479-717: The production of volatile organic compounds and phytohormones which play a significant role in plant defense mechanisms. In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell. Several horticultural crops are known to protect themselves against fungal plant pathogens with silica, to such a degree that fungicide application may fail unless accompanied by sufficient silicon nutrition. Silicaceous plant defense molecules activate some phytoalexins , meaning some of them are signalling substances producing acquired immunity . When deprived, some plants will substitute with increased production of other defensive substances. Life on Earth
19630-467: The pure element in the Earth's crust. It is widely distributed throughout space in cosmic dusts , planetoids , and planets as various forms of silicon dioxide (silica) or silicates . More than 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, often with very little processing of
19781-412: The pure element to exist in multiple chemical structures ( spatial arrangements of atoms ), known as allotropes , which differ in their properties. For example, carbon can be found as diamond , which has a tetrahedral structure around each carbon atom; graphite , which has layers of carbon atoms with a hexagonal structure stacked on top of each other; graphene , which is a single layer of graphite that
19932-428: The quantum dot, allowing electrons to transfer between them, filling the holes and preventing recombination. Fluorescence resonance energy transfer occurs when a complex forms between the quantum dot and a quencher molecule. The complex will continue to absorb light but when the energy is converted to the ground state it does not release a photon, quenching the material. The third method uses different approach by measuring
20083-772: The reactive nonmetals and the noble gases are nonmetals viewed in the broader sense. In some presentations, the halogens are not distinguished, with astatine identified as a metalloid and the others identified as nonmetals. Another commonly used basic distinction among the elements is their state of matter (phase), whether solid , liquid , or gas , at standard temperature and pressure (STP). Most elements are solids at STP, while several are gases. Only bromine and mercury are liquid at 0 degrees Celsius (32 degrees Fahrenheit) and 1 atmosphere pressure; caesium and gallium are solid at that temperature, but melt at 28.4°C (83.2°F) and 29.8°C (85.6°F), respectively. Melting and boiling points , typically expressed in degrees Celsius at
20234-419: The reducing agent. The spongy pieces of silicon thus produced are melted and then grown to form cylindrical single crystals, before being purified by zone refining . Other routes use the thermal decomposition of silane or tetraiodosilane ( SiI 4 ). Another process used is the reduction of sodium hexafluorosilicate , a common waste product of the phosphate fertilizer industry, by metallic sodium : this
20385-919: The remaining 11 elements have half lives too short for them to have been present at the beginning of the Solar System, and are therefore considered transient elements. Of these 11 transient elements, five ( polonium , radon , radium , actinium , and protactinium ) are relatively common decay products of thorium and uranium . The remaining six transient elements (technetium, promethium, astatine, francium , neptunium , and plutonium ) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements. Elements with atomic numbers 1 through 82, except 43 (technetium) and 61 (promethium), each have at least one isotope for which no radioactive decay has been observed. Observationally stable isotopes of some elements (such as tungsten and lead ), however, are predicted to be slightly radioactive with very long half-lives: for example,
20536-495: The same element having different numbers of neutrons are known as isotopes of the element. The number of protons in the nucleus also determines its electric charge , which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's chemical properties . The number of neutrons in a nucleus usually has very little effect on an element's chemical properties; except for hydrogen (for which
20687-404: The same number of protons in their nucleus), but having different numbers of neutrons . Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, said three isotopes are known as carbon-12 , carbon-13 , and carbon-14 ( C, C, and C). Natural carbon
20838-834: The same number of protons . The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules . Some elements are formed from molecules of identical atoms , e. g. atoms of hydrogen (H) form diatomic molecules (H 2 ). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of
20989-457: The second half of the 20th century, physics laboratories became able to produce elements with half-lives too short for an appreciable amount of them to exist at any time. These are also named by IUPAC, which generally adopts the name chosen by the discoverer. This practice can lead to the controversial question of which research group actually discovered an element, a question that delayed the naming of elements with atomic number of 104 and higher for
21140-496: The synthetically produced transuranic elements, available samples have been too small to determine crystal structures. Chemical elements may also be categorized by their origin on Earth, with the first 94 considered naturally occurring, while those with atomic numbers beyond 94 have only been produced artificially via human-made nuclear reactions. Of the 94 naturally occurring elements, 83 are considered primordial and either stable or weakly radioactive. The longest-lived isotopes of
21291-955: The table to illustrate recurring trends in the properties of the elements. The layout of the table has been refined and extended over time as new elements have been discovered and new theoretical models have been developed to explain chemical behavior. Use of the periodic table is now ubiquitous in chemistry, providing an extremely useful framework to classify, systematize and compare all the many different forms of chemical behavior. The table has also found wide application in physics , geology , biology , materials science , engineering , agriculture , medicine , nutrition , environmental health , and astronomy . Its principles are especially important in chemical engineering . The various chemical elements are formally identified by their unique atomic numbers, their accepted names, and their chemical symbols . The known elements have atomic numbers from 1 to 118, conventionally presented as Arabic numerals . Since
21442-430: The underlying mantle yields basaltic magmas and new ocean crust forms. This "ridge push" is one of the driving forces of plate tectonics, and it is constantly creating new ocean crust. Consequently, old crust must be destroyed, so opposite a spreading center, there is usually a subduction zone: a trench where an ocean plate is sinking back into the mantle. This constant process of creating a new ocean crust and destroying
21593-415: The underlying mantle asthenosphere are less dense than elsewhere on Earth and so are not readily destroyed by subduction. Formation of new continental crust is linked to periods of intense orogeny , which coincide with the formation of the supercontinents such as Rodinia , Pangaea and Gondwana . The crust forms in part by aggregation of island arcs including granite and metamorphic fold belts, and it
21744-561: The universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made. The first 94 elements have been detected directly on Earth as primordial nuclides present from the formation of the Solar System , or as naturally occurring fission or transmutation products of uranium and thorium. The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: all are radioactive, with short half-lives; if any of these elements were present at
21895-528: The work of Dmitri Mendeleev , a Russian chemist who published the first recognizable periodic table in 1869. This table organizes the elements by increasing atomic number into rows (" periods ") in which the columns (" groups ") share recurring ("periodic") physical and chemical properties . The periodic table summarizes various properties of the elements, allowing chemists to derive relationships between them and to make predictions about elements not yet discovered, and potential new compounds. By November 2016,
22046-477: The world's use of free silicon. Silicon is an important constituent of transformer steel , modifying its resistivity and ferromagnetic properties. The properties of silicon may be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys ( silumin alloys) for aluminium part casts , mainly for use in
22197-409: Was a silicon radio crystal detector, developed by American engineer Greenleaf Whittier Pickard in 1906. In 1940, Russell Ohl discovered the p–n junction and photovoltaic effects in silicon. In 1941, techniques for producing high-purity germanium and silicon crystals were developed for radar microwave detector crystals during World War II . In 1947, physicist William Shockley theorized
22348-475: Was likely repeatedly destroyed by large impacts, then reformed from the magma ocean left by the impact. None of Earth's primary crust has survived to today; all was destroyed by erosion , impacts, and plate tectonics over the past several billion years. Since then, Earth has been forming a secondary and tertiary crust, which correspond to oceanic and continental crust, respectively. Secondary crust forms at mid-ocean spreading centers , where partial-melting of
22499-459: Was not prepared until 31 years later, by Deville . By electrolyzing a mixture of sodium chloride and aluminium chloride containing approximately 10% silicon, he was able to obtain a slightly impure allotrope of silicon in 1854. Later, more cost-effective methods have been developed to isolate several allotrope forms, the most recent being silicene in 2010. Meanwhile, research on the chemistry of silicon continued; Friedrich Wöhler discovered
22650-442: Was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form. Its oxides form a family of anions known as silicates . Its melting and boiling points of 1414 °C and 3265 °C, respectively, are the second highest among all the metalloids and nonmetals, being surpassed only by boron . Silicon is the eighth most common element in the universe by mass, but very rarely occurs as
22801-551: Was synthesised by Charles Friedel and James Crafts in 1863, but detailed characterisation of organosilicon chemistry was only done in the early 20th century by Frederic Kipping . Starting in the 1920s, the work of William Lawrence Bragg on X-ray crystallography elucidated the compositions of the silicates, which had previously been known from analytical chemistry but had not yet been understood, together with Linus Pauling 's development of crystal chemistry and Victor Goldschmidt 's development of geochemistry . The middle of
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