All the remaining radioactive isotopes have half-lives that are less than seven seconds, and the majority of these have half-lives that are less than one tenth of a second.  With suitable organic substituents it is possible to produce stable polysilanes: they have surprisingly high electric conductivities, arising from sigma delocalisation of the electrons in the chain. It first gets a context handle into an LDAP namespace. Natural silicate compounds were also used in various types of mortar for construction of early human dwellings. , Due to the abundance of silicon in the Earth's crust, natural silicon-based materials had been used for thousands of years. The most widely used silicon device is the MOSFET (metal–oxide–semiconductor field-effect transistor), which has been manufactured in larger numbers than any other device in history. , Atalla's pioneering work on surface passivation and thermal oxidation culminated in his invention of the MOSFET (metal–oxide–silicon field-effect transistor), along with his Korean colleague Dawon Kahng, in 1959.  Silicon enters the ocean in a dissolved form such as silicic acid or silicate.  Silicon was given its present name in 1817 by Scottish chemist Thomas Thomson. The polyatomic ion name stays the same. β-tridymite slowly transforms to cubic β-cristobalite at about 1470 °C, which once again exists metastably below this transition temperature and transforms at 200–280 °C to α-cristobalite via small atomic displacements. In both cases, pure silicon was produced: the silicon dissolved in the molten aluminium, but crystallized upon cooling.  As a result, he is usually given credit for the element's discovery. Disilicon Hexabromide. Also significant are the garnets, [MII3MIII2(SiO4)3], in which the divalent cations (e.g.  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 is used in the chemical industry. It is relatively unreactive. The first working transistor was a point-contact transistor built by John Bardeen and Walter Brattain later that year while working under Shockley.  Lastly, because of 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. Standard organic reactions suffice to produce many derivatives; the resulting organosilanes are often significantly more reactive than their carbon congeners, readily undergoing hydrolysis, ammonolysis, alcoholysis, and condensation to form cyclic oligomers or linear polymers. Based upon that oxidation number, an electronic configuration is also given but note that for more exotic compounds you should view this as a guide only. 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 the world's use of free silicon. Silicon is a component of some superalloys. Molar Mass. , 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. Since sulfur and iodine are nonmetals, this is a binary molecular compound. disulfur. The latter usually do not react with aqueous reagents, except for hydrofluoric acid; however, they do react with much more aggressive reagents such as liquid potassium hydroxide, or gaseous fluorine or chlorine when red-hot. Silicon carbide is rapidly attacked by chlorine gas, which forms SiCl4 and carbon at 100 °C and SiCl4 and CCl4 at 1000 °C. The Southern Ocean produces about one-third of global marine biogenic silica. Zou, Hui, Tao Wang, Junzhao Yuan, Jian Sun, Yan Yuan, Jianhong Gu, Xuezhong Liu, Jianchun Bian, and Zongping Liu.  In its diamond-like behavior it serves as an illustration of the chemical similarity between carbon and silicon. A transistor is an n-p-n junction, with a thin layer of weakly p-type silicon between two n-type regions. , The word "silicone" was first used by Frederic Kipping in 1901. More than 90% of 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. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. It is also ammonolysed quickly and completely by liquid ammonia as follows to form an imide:, It reacts with the sulfides of sodium, magnesium, aluminium, and iron to form metal thiosilicates: reaction with ethanol results in tetraethylsilicate Si(OEt)4 and hydrogen sulfide. Unbranched and branched chains are known up to n=8, and the cycles Si5H10 and Si6H12 are also known. 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. An estimated 15% of the world production of metallurgical grade silicon is further refined to semiconductor purity. Many of these have direct commercial uses, such as clays, silica sand, and most kinds of building stone. Despite the double bond rule, stable organosilanethiones RR'Si=S have been made thanks to the stabilising mechanism of intermolecular coordination via an amine group. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide).  When diatom cells are lysed in the upper ocean, their nutrients like, iron, zinc, and silicon, are brought to the lower ocean through a process called marine snow. Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of cementite where exposed to outside air. They are much more reactive than the corresponding alkanes, because of the larger radius of silicon compared to carbon facilitating nucleophilic attack at the silicon, the greater polarity of the Si–H bond compared to the C–H bond, and the ability of silicon to expand its octet and hence form adducts and lower the reaction's activation energy. Silicon (IV) Dioxide. Silicon is in group 4A, so it has 4 valence electrons and an oxidation state of +4. Chemistry is the study of the structures, physical properties, and chemical properties of material substances. , The "Silicon Age" refers to the late 20th century to early 21st century. Other high-pressure forms of silica are known, such as coesite and stishovite: these are known in nature, formed under the shock pressure of a meteorite impact and then rapidly quenched to preserve the crystal structure. Diatoms uses silicon in the biogenic silica (BSIO2) form, which is taken up by the silicon transport protein (SIT) to be predominantly used in the cell wall structure as frustules.  Atalla's surface passivation process is considered the most important advance in silicon semiconductor technology, paving the way for the mass-production of silicon semiconductor devices. In compounds of silicon (where known), the most common oxidation numbers of silicon are: 4, and -4. If either the cation or the anion was a polyatomic ion, the polyatomic ion name is used in the name of the overall compound. For example, (Me3Si)2O is valuable for the preparation of derivatives of molybdenum and tungsten oxyhalides, converting a tungsten hexachloride suspension in dichloroethane solution quantitatively to WOCl4 in under an hour at room temperature, and then to yellow WO2Cl2 at 100 °C in light petroleum at a yield of 95% overnight. , The silanes comprise a homologous series of silicon hydrides with a general formula of SinH2n + 2.  The reaction of silicon fluoride with excess hydrofluoric acid produces the octahedral hexafluorosilicate anion SiF2−6. , Crystalline bulk silicon is rather inert, but becomes more reactive at high temperatures.  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. Many hydrates and silicic acids exist in the most dilute of aqueous solutions, but these are rather insoluble and quickly precipitate and condense and cross-link to form various polysilicic acids of variable combinations following the formula [SiOx(OH)4−2x]n, similar to the behaviour of boron, aluminium, and iron, among other elements. 1. sulfur carbonate 2. sulfur carbide 3. silicon carbide 4. silicon carbonate 5. silicon carbonite 6. silicate carbonate 7. silicate carbide  The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. Thus, the compound formed from sodium and chlorine will be ionic (a metal and a non-metal).