query: name an element of group 18 which can form compounds

pos: Noble gas compound Noble gas compound Noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon. From the standpoint of chemistry, the noble gases may be divided into two groups: the relatively reactive krypton (ionisation energy 14.0 eV), xenon (12.1 eV), and radon (10.7 eV) on one side, and the very unreactive argon (15.8 eV), neon (21.6 eV), and helium (24.6 eV) on the other. Consistent with this classification, Kr, Xe, and Rn form

pos: Noble gas compound of Ar, Kr, and Xe. (For instance, radioactive isotopes of krypton and xenon are difficult to store and dispose, and compounds of these elements may be more easily handled than the gaseous forms.) In addition, clathrates of radioisotopes may provide suitable formulations for experiments requiring sources of particular types of radiation; hence. Kr clathrate provides a safe source of beta particles, while Xe clathrate provides a useful source of gamma rays. Noble gas compound Noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally

pos: Period 4 element a halogen, never existing in pure form in nature. Bromine is barely liquid at room temperature, boiling at about 330 kelvins. Bromine is also quite toxic and corrosive, but bromide ions, which are relatively inert, can be found in halite, or table salt. Bromine is often used as a fire retardant because many compounds can be made to release free bromine atoms. Krypton (Kr) is a noble gas, placed under argon and over xenon. Being a noble gas, krypton rarely interacts with itself or other elements; although compounds have been detected, they are all unstable and decay rapidly, and as

pos: Xenon from the decay of mantle-derived gases from soon after Earth's formation. After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds, a large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the electronegative atoms fluorine or oxygen. The chemistry of xenon in each oxidation state is analogous to that of the neighboring element iodine in the immediately lower oxidation state. Three fluorides are known: , , and . XeF is theorized to be unstable. These are the starting points for the synthesis of almost all xenon compounds. The solid, crystalline difluoride

neg: Compounds of fluorine gases (helium through argon) do not form stable binary fluorides. Argon forms no binary fluoride, but reacts in extreme conditions with hydrogen fluoride to form argon fluorohydride; it is the only "stable" argon compound. Helium and neon do not form any stable chemical compounds at all. Helium forms helium fluorohydride; it has been shown to be unstable in gas phase, but there are specific conditions for which it may be stable. Neon, the least reactive element, is not now expected to form a stable compound capable of synthesis. Oganesson, the last currently known group 18 element, is predicted to form

neg: Cr23C6 crystal structure neighbors are included. Examples of compounds that form in this structure type include CrC, MnC, and many ternary intermetallic carbides and borides. A few phases of ternary silicides, germanides, and phosphides are also known to exist. In going from the binary to ternary systems, some of the transition metal atoms are substituted by a third element, which can be an alkali metal, alkaline earth metal, rare-earth element, main group element, or another transition metal. This leads to an empirical formula of the form ABC. Materials of this kind continue to be studied for potentially interesting magnetic and physical properties. Cr23C6

neg: Binary compounds of silicon Other known stable fluorides in this group are SiF, SiF (liquid) and polymeric solids known as polysilicon fluorides (SiF) and (SiF). The other halides form similar binary silicon compounds. > Binary compounds of silicon Binary compounds of silicon are binary chemical compounds containing silicon and one other chemical element. Technically the term silicide is reserved for any compounds containing silicon bonded to a more electropositive element. Binary silicon compounds can be grouped into several classes. Saltlike silicides are formed with the electropositive s-block metals. Covalent silicides and silicon compounds occur with hydrogen and the elements in groups 10 to 17.

neg: Binary compounds of silicon Binary compounds of silicon Binary compounds of silicon are binary chemical compounds containing silicon and one other chemical element. Technically the term silicide is reserved for any compounds containing silicon bonded to a more electropositive element. Binary silicon compounds can be grouped into several classes. Saltlike silicides are formed with the electropositive s-block metals. Covalent silicides and silicon compounds occur with hydrogen and the elements in groups 10 to 17. Transition metals form metallic silicides with some exceptions: silver, gold and the group 12 elements. The general composition is MSi or MSi with n ranging from 1 to 6. Examples

neg: Oxohalide Oxohalide Molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOX, X = F, Cl, Br, I. The element A may be a main group element, a transition element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure. Oxohalides can be seen as compounds intermediate between oxides and halides. There are three general methods of synthesis: In addition,

neg: Boron group oxide (AlO and GaO respectively) are amphoteric, indium(III) oxide (InO) is nearly amphoteric, and thallium(III) oxide (TlO) is a Lewis base because it dissolves in acids to form salts. Each of these compounds are stable, but thallium oxide decomposes at temperatures higher than 875 °C. The elements in group 13 are also capable of forming stable compounds with the halogens, usually with the formula MX (where M is a boron-group element and X is a halogen.) The only exception to this is thallium(III) iodide. Fluorine, the first halogen, is able to form stable compounds with every element that has been

neg: Nitrogen is instead used in many languages, such as French, Russian, and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds. Nitrogen is the lightest member of group 15 of the periodic table, often called the pnictogens. The name comes from the Greek πνίγειν "to choke", directly referencing nitrogen's asphyxiating properties. It is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless

neg: Compounds of zinc Compounds of zinc Compounds of zinc are chemical compounds containing the element zinc which is a member of the group 12 of the periodic table. The oxidation state of most compounds is the group oxidation state of +2. Zinc may be classified as a post-transition main group element with zinc(II). Zinc compounds are noteworthy for their nondescript behavior, they are generally colorless, do not readily engage in redox reactions, and generally adopt symmetrical structures. In its compounds, Zn ions have an electronic configuration [Ar]3d. As such, its complexes tend to be symmetrical, ZnO and zinc sulfide, ZnS, (zincblende) in which

neg: Arsenide the mineral, arsenic is immobile and poses no environmental risk. Released from the mineral, arsenic is poisonous and mobile. Partial reduction of arsenic with alkali metals (and related electropositive elements) affords polyarsenic compounds, which are members of the Zintl phases. Arsenide In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Many metals form binary compounds containing arsenic, and these are called arsenides. They exist with many stoichiometries, and in this respect arsenides are similar to phosphides. The group 1 alkali metals and the group 2, alkaline earth metals, form arsenides with isolated arsenic

neg: Oxohalide elements iron, antimony, bismuth and lanthanum form oxochlorides of general formula MOCl. MOBr and MOI are also known for Sb and Bi. Many of their crystal structures have been determined. Oxohalide Molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOX, X = F, Cl, Br, I. The element A may be a main group element, a transition element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with

neg: Inorganic chemistry group 3 or 12 are sometimes also incorporated into this group, but also often classified as main group compounds. Transition metal compounds show a rich coordination chemistry, varying from tetrahedral for titanium (e.g., TiCl) to square planar for some nickel complexes to octahedral for coordination complexes of cobalt. A range of transition metals can be found in biologically important compounds, such as iron in hemoglobin. Usually, organometallic compounds are considered to contain the M-C-H group. The metal (M) in these species can either be a main group element or a transition metal. Operationally, the definition of an organometallic compound is

neg: Period 2 element the third most abundant by number of atoms. There are an almost infinite number of compounds that contain carbon due to carbon's ability to form long stable chains of C — C bonds. The simplest carbon-containing molecules are the hydrocarbons, which contain carbon and hydrogen, although they sometimes contain other elements in functional groups. Hydrocarbons are used as fossil fuels and to manufacture plastics and petrochemicals. All organic compounds, those essential for life, contain at least one atom of carbon. When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds including sugars, lignans, chitins, alcohols,

neg: Oxygen Oxygen Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula . Diatomic oxygen gas constitutes 20.8% of the Earth's atmosphere. As compounds including oxides, the element

neg: Period 1 element than hydrogen production from natural gas. The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons. In ionic compounds, it can take on either a positive charge, becoming a cation composed of a bare proton, or a negative charge, becoming an anion known as a hydride. Hydrogen can form compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. As the only neutral atom for which the Schrödinger

neg: Ytterbium resulting fumes are hazardous. Ytterbium fires cannot be extinguished using water, and only dry chemical class D fire extinguishers can extinguish the fires. Ytterbium Ytterbium is a chemical element with symbol Yb and atomic number 70. It is the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the other lanthanides, its most common oxidation state is +3, as in its oxide, halides, and other compounds. In aqueous solution, like compounds of other late lanthanides, soluble ytterbium compounds form complexes with nine water molecules. Because of

neg: Group 12 element metal-metal bond and a diamagnetic species. Cadmium can also form species such as [CdCl] in which the metal's oxidation state is +1. Just as with mercury, the formation of a metal-metal bond results in a diamagnetic compound in which there are no unpaired electrons; thus, making the species very reactive. Zinc(I) is known only in the gas phase, in such compounds as linear ZnCl, analogous to calomel. The elements in group 12 are usually considered to be d-block elements, but not transition elements as the d-shell is full. Some authors classify these elements as main-group elements because the valence electrons

neg: Binary compounds of silicon silicon by weight (18% atom percent) without mutual solubility in the solid state. Silver forms another eutectic at 835 °C with 11% silicon by weight, again with negligible mutual solid state solubility. In group 12 all elements form a eutectic close to the metal melting point without mutual solid-state solubility: zinc at 419 °C and > 99 atom percent zinc and cadmium at 320 °C (< 99% Cd). Commercially relevant intermetallics are group 6 molybdenum disilicide, a commercial ceramic mostly used as an heating element. Tungsten disilicide is also a commercially available ceramic with uses in microelectronics. Platinum silicide is

neg: Period 6 element a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains in rocks, in veins and in alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium. Gold resists attacks by individual acids, but it can be dissolved by the aqua regia (nitro-hydrochloric acid), so named because it dissolves gold. Gold

neg: Group 6 element The metals form compounds in different oxidation states: chromium forms compounds in all states from −2 to +6: disodium pentacarbonylchromate, disodium decacarbonyldichromate, bis(benzene)chromium, tripotassium pentanitrocyanochromate, chromium(II) chloride, chromium(III) oxide, chromium(IV) chloride, potassium tetraperoxochromate(V), and chromium(VI) dichloride dioxide; the same is also true for molybdenum and tungsten, but the stability of the +6 state grows down the group. Depending on oxidation states, the compounds are basic, amphoteric, or acidic; the acidity grows with the oxidation state of the metal. Tungsten has no known biological role in the human body. Seaborgium's high radioactivity would make it a toxic element, due to radiation

neg: Pnictogen These are in the form of REMPn, where M is a carbon group or boron group element and Pn is any pnictogen except nitrogen. These compounds are between ionic and covalent compounds and thus have unusual bonding properties. These elements are also noted for their stability in compounds due to their tendency for forming double and triple covalent bonds. This is the property of these elements which leads to their potential toxicity, most evident in phosphorus, arsenic and antimony. When these substances react with various chemicals of the body, they create strong free radicals not easily processed by the liver,

neg: Acryloyl group Acryloyl group In organic chemistry, the acryloyl group is form of enone with structure HC=CH–C(=O)–; it is the acyl group derived from acrylic acid. The preferred IUPAC name for the group is prop-2-enoyl, and it is also (less correctly) known as acrylyl or simply acryl. Compounds containing an acryloyl group can be referred to as "acrylic compounds". An acrylic compound is typically an α,β-unsaturated carbonyl compound: it contains a carbon–carbon double bond and a carbon–oxygen double bond (carbonyl) separated by a carbon–carbon single bond, thus possessing properties characteristic for both functional groups : In addition, since both double bonds are

neg: Apicophilicity positions. The use of multidentate ligands can also control the arrangement of substituents. For example, a bidentate ligand with a five-membered ring structure greatly stabilizes the arrangement in which their two coordination sites occupy equatorial and an apical position. Apicophilicity Apicophilicity is the phenomenon in which electronegative substituents of trigonal bipyramidal pentacoordinate compounds prefer to occupy apical positions (L). The term "apicophilicity" was first proposed by Earl L. Muetterties in 1963 for the structural analysis of pentacoordinate phosphorus fluorides by F NMR. Since the apical bonding of a pentacoordinate typical (group 1, 2, 13-18) element compound consists of a 3-center-4-electron

neg: Flavonoid biosynthesis Flavanoids can possess chiral carbons. Methods of analysis should take this element into account especially regarding bioactivity or enzyme stereospecificity. The biosynthesis of flavonoids involves several enzymes. Flavonoid biosynthesis Flavonoids are synthesized by the phenylpropanoid metabolic pathway in which the amino acid phenylalanine is used to produce 4-coumaroyl-CoA. This can be combined with malonyl-CoA to yield the true backbone of flavonoids, a group of compounds called chalcones, which contain two phenyl rings. Conjugate ring-closure of chalcones results in the familiar form of flavonoids, the three-ringed structure of a flavone. The metabolic pathway continues through a series of enzymatic modifications to

neg: Arsenide Arsenide In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Many metals form binary compounds containing arsenic, and these are called arsenides. They exist with many stoichiometries, and in this respect arsenides are similar to phosphides. The group 1 alkali metals and the group 2, alkaline earth metals, form arsenides with isolated arsenic atoms. They form upon heating arsenic powder with excess sodium gives sodium arsenide (NaAs). The structure of NaAs is complex with unusually short Na–Na distances of 328–330 pm which are shorter than in sodium metal. This short distance indicates the

neg: Acryloyl group separated by a single C–C bond, the double bonds are conjugated. Acryloyl group In organic chemistry, the acryloyl group is form of enone with structure HC=CH–C(=O)–; it is the acyl group derived from acrylic acid. The preferred IUPAC name for the group is prop-2-enoyl, and it is also (less correctly) known as acrylyl or simply acryl. Compounds containing an acryloyl group can be referred to as "acrylic compounds". An acrylic compound is typically an α,β-unsaturated carbonyl compound: it contains a carbon–carbon double bond and a carbon–oxygen double bond (carbonyl) separated by a carbon–carbon single bond, thus possessing properties characteristic for

neg: John Dalton multiple proportions appears to be anticipated in the words: But there is reason to suspect that this sentence may have been added some time after the reading of the paper, which was not published until 1805. Compounds were listed as binary, ternary, quaternary, etc. (molecules composed of two, three, four, etc. atoms) in the "New System of Chemical Philosophy" depending on the number of atoms a compound had in its simplest, empirical form. Dalton hypothesised the structure of compounds can be represented in whole number ratios. So, one atom of element X combining with one atom of element Y is

neg: Binary compounds of hydrogen Binary compounds of hydrogen Binary compounds of hydrogen are binary chemical compounds containing just hydrogen and one other chemical element. By convention all binary hydrogen compounds are called hydrides even when the hydrogen atom in it is not an anion. These hydrogen compounds can be grouped into several types. Binary hydrogen compounds in group 1 are the ionic hydrides (also called saline hydrides) wherein hydrogen is bound electrostatically. Because hydrogen is located somewhat centrally in an electronegative sense, it is necessary for the counterion to be exceptionally electropositive for the hydride to possibly be accurately described as truly behaving ionic.

neg: Boron group The next group-13 elements, aluminium and gallium, form fewer stable hydrides, although both AlH and GaH exist. Indium, the next element in the group, is not known to form many hydrides, except in complex compounds such as the phosphine complex HInP(Cy). No stable compound of thallium and hydrogen has been synthesized in any laboratory. All of the boron-group elements are known to form a trivalent oxide, with two atoms of the element bonded covalently with three atoms of oxygen. These elements show a trend of increasing pH (from acidic to basic). Boron oxide (BO) is slightly acidic, aluminium and gallium

neg: Boron group characteristics. Boron differs from the other group members in its hardness, refractivity and reluctance to participate in metallic bonding. An example of a trend in reactivity is boron's tendency to form reactive compounds with hydrogen. Most of the elements in the boron group show increasing reactivity as the elements get heavier in atomic mass and higher in atomic number. Boron, the first element in the group, is generally unreactive with many elements except at high temperatures, although it is capable of forming many compounds with hydrogen, sometimes called "boranes". The simplest borane is diborane, or BH. Another example is BH.

neg: Dakin oxidation basic conditions. In "o"-hydroxy compounds, when the hydroxyl group is protonated, an intramolecular hydrogen bond can form between the hydroxyl hydrogen and the carbonyl oxygen, stabilizing a resonance structure with positive charge on the carbonyl carbon, thus increasing the carbonyl carbon’s electrophilicity (7). Lacking this stabilization, the carbonyl carbon of "p"-hydroxy compounds is less electrophilic. Therefore, "o"-hydroxy compounds are oxidized faster than "p"-hydroxy compounds when the hydroxyl group is protonated. "M"-hydroxy compounds do not oxidize to "m"-benzenediols and carboxylates. Rather, they form phenyl carboxylic acids. Variations in the aryl rings' migratory aptitudes can explain this. Hydroxyl groups "ortho" or "para"

neg: Period 3 element phosphorus originates from oxidation of the white (but not red) phosphorus and should be called chemiluminescence. It is also the lightest element to easily produce stable exceptions to the octet rule. The vast majority of phosphorus compounds are consumed as fertilizers. Other applications include the role of organophosphorus compounds in detergents, pesticides and nerve agents, and matches. "Sulfur" (symbol S) is an abundant, multivalentnon-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S. Elemental sulfur is a bright yellow crystalline solid when at room temperature. Chemically, sulfur can react as either an oxidant or reducing agent.

neg: Diphosphenes the carbene addition reaction of C=C double bonds, diphosphene can form a P-C-P three-membered ring with dihalocarbene <chem>:CCl2</chem> or <chem>:CBr2</chem>. Diphosphiranes can further rearrange to 1,3-diphospha-allene via ring opening reactions by using MeLi or n-BuLi. Cleavage of C=C double bonds is very common and important in organic chemistry while that of unsaturated bonds between heavy Group 14 and Group 15 elements are lack of investigation. Successful polarization of Si-Si multiple bonds reveals potential interconversion between formula_7 -bonding electrons and lone-pair electrons in heavy Group 14 and Group 15 compounds that contain multiple bonds. Diphosphene, as the typical heavy-element multiple bonds

neg: Period 4 element can also be found in semiconductors. Germanium (Ge) is an element in period 4, between gallium and arsenic. Germanium, like silicon above it, is an important semiconductor and is commonly used in diodes and transistors, often in combination with arsenic. Germanium is fairly rare on Earth, leading to its comparatively late discovery. Germanium, in compounds, can sometimes irritate the eyes, skin, or lungs. Arsenic (As) is an element in period 4, between germanium and selenium. Arsenic, as mentioned above, is often used in semiconductors in alloys with germanium. Arsenic, in pure form and some alloys, is incredibly poisonous to all

neg: Antinutrient absorption of iron via an unclear mechanism involving iron transport protein hDMT1, which calcium can inhibit. Some proteins can also be antinutrients, such as the trypsin inhibitors and lectins found in legumes. These enzyme inhibitors interfere with digestion. Avidin is an antinutrient found in active form in raw egg whites. It binds very tightly to biotin (vitamin B7) and can cause deficiency of B7 in animals and, in extreme cases, in humans. Widespread form of antinutrients are the flavonoids, which are a group of polyphenolic compounds that include tannins. These compounds chelate metals such as iron and zinc and reduce

neg: Halide compounds. Examples of halide compounds are: Halide A halide is a binary phase, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluoride, chloride, bromide, iodide, astatide, or theoretically tennesside compound. The alkali metals combine directly with halogens under appropriate conditions forming halides of the general formula, MX (X = F, Cl, Br or I). Many salts are halides; the "hal-" syllable in "halide" and "halite" reflects this correlation. All Group 1 metals form halides that are white solids

neg: Azo compound Azo compound Azo compounds are compounds bearing the functional group diazenyl R−N=N−R′, in which R and R′ can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more stable derivatives contain two aryl groups. The N=N group is called an "azo group". The name azo comes from "azote," the French name for nitrogen that is derived from the Greek ("a-", "not") + ("zōē", life). Many textile and leather articles are dyed with azo dyes and pigments. Aryl azo compounds are

neg: Plumbide Plumbides can also be Zintl phase compounds, such as [K(18-crown-6)]KPb·(en). This is not a simple Zintl compound, but rather contains the organic molecules 18-crown-6 and ethylenediamine (en) in order to stabilize the crystal structure. Plumbide A plumbide can refer to one of two things: an intermetallic compound that contains lead, or a Zintl phase compound with lead as the anion. Plumbides can be formed when lead forms a Zintl phase compound with a more metallic element. One salt that can be formed this way is when cryptand reacts with sodium and lead in ethylenediamine (en) to produce [Pb], which is

neg: Allyl group enantioselectivity. If a one-pot metal insertion and allylation procedure is required, indium- mediated allylation is an attractive option for generating homoallylic alcohols directly from allyl halides and carbonyl compounds. In general, the method is called the Barbier reaction, and can employ a variety of metals such as magnesium, aluminium, zinc, indium, and tin. The reaction is often used as a milder form of the Grignard addition reaction, and can often tolerate aqueous solvents Many substituents can be attached to the allyl group to give stable compounds. Commercially important allyl compounds include: Allyl group An allyl group is a substituent with

neg: Azo compound Union countries in September 2003. As only a small number of dyes contained an equally small number of amines, relatively few products were affected. Azo compound Azo compounds are compounds bearing the functional group diazenyl R−N=N−R′, in which R and R′ can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more stable derivatives contain two aryl groups. The N=N group is called an "azo group". The name azo comes from "azote," the French name for nitrogen that is derived

neg: Organomanganese chemistry with methyllithium followed by addition of TMED. Methylcyclopentadienyl manganese tricarbonyl is a half-sandwich compound used as a gasoline additive. In the same group 7 elements technetium is a radioactive synthetic element and little explored. Organorhenium compounds can be found with oxidation states +4 and +5. An important starting material is dirhenium decacarbonyl, which can be synthesized by carbonylation of rhenium(VII) oxide. Methylrhenium trioxide is used as a catalyst. Organomanganese chemistry Organomanganese chemistry is the chemistry of organometallic compounds containing a carbon to manganese chemical bond. In a recent review Cahiez et al. argue that as manganese is cheap and benign

neg: Fluoride describe compounds which release fluoride upon dissolving. Hydrogen fluoride is itself an example of a non-systematic name of this nature. However, it is also a trivial name, and the preferred IUPAC name for "fluorane". Fluorine is estimated to be the 13th most abundant element in the earth's crust and is widely dispersed in nature, almost entirely in the form of fluorides. Many minerals are known, but of paramount commercial importance is fluorite (CaF), which is roughly 49% fluoride by mass. The soft, colorful mineral is found worldwide. Fluoride is naturally present at low concentration in most fresh and saltwater sources

neg: Atargatis near Akko an altar is inscribed "to Adado and Atargatis, the gods who listen to prayer"; and the full name "ʿtrʿth" appears on a bilingual inscription found in Palmyra. The name "ʿAtarʿatheh" is widely held to derive from a compound of the Aramaic form "ʿAttar", which is a cognate of "ʿAțtart" minus its feminine suffix "-t", plus "ʿAttah" or "ʿAtā", a cognate of "ʿAnat". Alternatively, the second half may be a Palmyrene divine name "ʿAthe" (i.e. "tempus opportunum"), which occurs as part of many compounds. It has also been proposed that the element "-gatis" may relate to the Greek "gados"

neg: Hungarian orthography suffix). The same rule is applied to compounds with three or more elements, although compounds with more than four elements are simplified (lower-ranked hyphens are removed). An en dash is used to express a relation between two places, and its adjectival form becomes completely lower-case (e.g. "Moszkva–Párizs" ‘Moscow-Paris [route]’ and "moszkva–párizsi" ‘of the Moscow-Paris route’). However, if a higher-ranked connected element becomes an adjective, the geographical proper names will retain the upper case (e.g. "Volga–Don-csatorna" ‘Volga-Don canal’ vs. "Volga–Don-csatornai"), except when the elements of the name contain adjectives or common nouns, which will become lower-case (e.g. "Cseh–Morva-dombság" ‘Bohemian-Moravian Highlands’ vs.

neg: Silver halide Silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to produce silver bromide (AgBr), silver chloride (AgCl), silver iodide (AgI), and three forms of silver fluoride, respectively. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX. Although most silver halides involve silver atoms with oxidation states of +1 (Ag), silver halides in which the silver atoms have oxidation states of

neg: Justus von Liebig of carbon, hydrogen, and oxygen atoms can behave like an element, take the place of an element, and can be exchanged for elements in chemical compounds. This laid the foundation for the doctrine of compound radicals, which can be seen as an early step in the development of structural chemistry. The 1830s were a period of intense investigation of organic compounds by Liebig and his students, and of vigorous debate about the theoretical implications of their results. Liebig published on a wide variety of topics, personally averaging 30 papers per year between 1830 and 1840. Liebig not only isolated individual

neg: Turkish phonology unaccented, with all the syllables on the same pitch. Suffixes such as "-di" and "-se/-sa" are not pre-accenting if they are added directly to the verb stem: This accentual pattern can disambiguate homographic words containing possessive suffixes or the plural suffix: Compound nouns are usually accented on the first element only. Any accent on the second element is lost, just as in English compounds such as "police-station", where the second element has no accent: The same is true of compound and intensive adjectives: Some compounds, however, are accented on the final, for example those of the form verb-verb or subject-verb:

neg: Hungarian orthography proper name, e.g. "New York állam" ‘State of New York’ vs. "New York állami". However, if the first element of such an entity is a common noun or an adjectival form, all elements are written lower case (e.g. in names of local administrative units like "Váci kistérség" vs. "váci kistérségi"). Names of public spaces (roads, streets, squares, bridges etc.) are written separately (except for elements that are already compounds or hyphenated). Their first element is capitalized, and this capitalization is kept even in the adjectival forms, e.g. "Váci utca" ‘Váci Street’ and "Váci utcai." If a common name is added

neg: Ozonolysis Ozonolysis Ozonolysis is an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone. Alkenes and alkynes form organic compounds in which the multiple carbon–carbon bond has been replaced by a carbonyl group while azo compounds form nitrosamines. The outcome of the reaction depends on the type of multiple bond being oxidized and the work-up conditions. Alkenes can be oxidized with ozone to form alcohols, aldehydes or ketones, or carboxylic acids. In a typical procedure, ozone is bubbled through a solution of the alkene in methanol at −78 °C until the solution takes on

neg: Flavin group Flavin group Flavin (from Latin "flavus", "yellow") is the common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine. The biochemical source is the vitamin riboflavin. The flavin moiety is often attached with an adenosine diphosphate to form flavin adenine dinucleotide (FAD), and, in other circumstances, is found as flavin mononucleotide (or FMN), a phosphorylated form of riboflavin. It is in one or the other of these forms that flavin is present as a prosthetic group in flavoproteins. The flavin group is capable of undergoing oxidation-reduction reactions, and can accept either one electron

neg: Plant nutrition one element may present as symptoms of toxicity from another element, and vice versa. An abundance of one nutrient may cause a deficiency of another nutrient. For example, K uptake can be influenced by the amount of NH available. Although nitrogen is plentiful in the Earth's atmosphere, relatively few plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form). Most plants, therefore, require nitrogen compounds to be present in the soil in which they grow. Carbon and oxygen are absorbed from the air while other nutrients are absorbed from the soil. Green plants obtain their carbohydrate

neg: Carbon diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form

neg: Silver halide with silver halide optical fibers for transmitting mid-infrared light from carbon dioxide lasers. The fibers allow laser welding of human tissue, as an alternative to traditional sutures. Silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to produce silver bromide (AgBr), silver chloride (AgCl), silver iodide (AgI), and three forms of silver fluoride, respectively. As a group, they are often referred to as the silver halides, and are often given the

neg: Halogen only periodic table group that contains elements in three of the main states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens, that is chlorine, bromine and iodine, are often used as disinfectants. Organobromides are the most important class of flame retardants. Elemental halogens are dangerous and can be lethally toxic. The fluorine mineral fluorospar was known as early as 1529. Early chemists realized that fluorine compounds contain an undiscovered element, but were unable to isolate it. In 1860, George

neg: Helium compounds Helium compounds Helium is the most unreactive element, so it was commonly believed that helium compounds do not exist at all. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, and in this form the atom does not readily accept any extra electrons or join with anything to make covalent compounds. The electron affinity is 0.080 eV, which is very close to zero. The helium atom is small with the radius of the outer electron shell at 0.29 Å. The atom is very hard with a Pearson's hardness of

neg: Solid solution strengthening Solid solution strengthening Solid solution strengthening is a type of alloying that can be used to improve the strength of a pure metal. The technique works by adding atoms of one element (the alloying element) to the crystalline lattice of another element (the base metal), forming a solid solution. The local nonuniformity in the lattice due to the alloying element makes plastic deformation more difficult by impeding dislocation motion. In contrast, alloying beyond the solubility limit can form a second phase, leading to strengthening via other mechanisms (e.g. the precipitation of intermetallic compounds). Depending on the size of the alloying

neg: Nickel compounds Nickel compounds Compounds of nickel are chemical compounds containing the element nickel which is a member of the group 10 of the periodic table. Most compounds in the group have an oxidation state of +2. Nickel is classified as a transition metal with nickel(II) having much chemical behaviour in common with iron(II) and cobalt(II). Many salts of nickel(II) are isomorphous with salts of magnesium due to the ionic radii of the cations being almost the same. Nickel forms many coordination complexes. Nickel tetracarbonyl was the first pure metal carbonyl produced, and is unusual in its volatility. Metalloproteins containing nickel are

neg: Chemical nomenclature Therefore, the name of the compound is calcium hydroxide. If one is asked to write the formula for copper(I) chromate, the Roman numeral indicates that copper ion is Cu and one can identify that the compound contains the chromate ion (). Two of the 1+ copper ions are needed to balance the charge of one 2− chromate ion, so the formula is CuCrO. Type-III binary compounds are covalently bonded. Covalent bonding occurs between nonmetal elements. Covalently-bonded compounds are also known as "molecules". In the compound, the first element is named first and with its full elemental name. The second element

neg: Bismuth(III) nitrate Bismuth(III) nitrate Bismuth(III) nitrate a salt composed of bismuth in its cationic +3 oxidation state and nitrate anions. The most common solid form is the pentahydrate. It is used in the synthesis of other bismuth compounds. It is available commercially. It is the only nitrate salt formed by a group 15 element, indicative of bismuth's metallic nature. Bismuth nitrate can be prepared by the reaction of bismuth metal and concentrated nitric acid. It dissolves in nitric acid but is readily hydrolysed to form a range of oxynitrates when the pH increases above 0. It is also soluble in acetone, acetic

neg: Period 5 element 40. The name of zirconium is taken from the mineral "zircon". Its atomic mass is 91.224. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is mainly used as a refractory and opacifier, although minor amounts are used as alloying agent for its strong resistance to corrosion. Zirconium is obtained mainly from the mineral zircon, which is the most important form of zirconium in use. Zirconium forms a variety of inorganic and organometallic compounds such as zirconium dioxide and zirconocene dichloride, respectively. Five isotopes occur naturally, three of which are stable. Zirconium compounds have no biological role.

neg: Group 12 element complex compounds. Unlike other metals, cadmium is resistant to corrosion and as a result it is used as a protective layer when deposited on other metals. As a bulk metal, cadmium is insoluble in water and is not flammable; however, in its powdered form it may burn and release toxic fumes. Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p,

neg: IUPAC nomenclature of inorganic chemistry 2005 and reflect either the empirical formula or the molecular formula. The ordering of the elements follows the formal electronegativity list for binary compounds and electronegativity list to group the elements into two classes which are then alphabetically sequenced. The proportions are specified by di-, tri-, etc. (See IUPAC numerical multiplier.) Where there are known to be complex cations or anions these are named in their own right and then these names used as part of the compound name. In binary compounds the more electropositive element is placed first in the formula. The formal list is used. The name of the

neg: Benzenediol the aromatic ring of a benzenediol are weakly acidic. Each benzenediol can lose an H from one of the hydroxyls to form a type of phenolate ion. The Dakin oxidation is an organic redox reaction in which an ortho- or para-hydroxylated phenyl aldehyde or ketone reacts with hydrogen peroxide in base to form a benzenediol and a carboxylate. Overall, the carbonyl group is oxidized, and the hydrogen peroxide is reduced. Benzenediol Benzenediols or dihydroxybenzenes are organic chemical compounds in which two hydroxyl groups are substituted onto a benzene ring. These aromatic compounds are classed as phenols. There are three isomers

neg: Phosphorine similar, phosphorines are far less basic. The pK's of CHPH and CHNH are respectively -16.1 and 5.2. Methyl lithium adds to phosphorus in phosphorine whereas it adds to the 2-position of pyridine. Phosphorine undergoes electrophilic substitution reactions like ordinary aromatic compounds: bromination, acylation, and so on. Coordination complexes bearing phosphorine as a [ligand] are known. Phosphorines can bind to metals through phosphorus center. Complexes of the diphospha analogue of bipyridine are known. Phosphorines also form pi-complexes, illustrated by V(η-CHP). Phosphorine Phosphorine (IUPAC name: phosphinine) is a heavier element analog of pyridine, containing a phosphorus atom instead of an aza- moiety.

neg: Amine of aromatic amines such as aniline ("phenylamine") (A = aryl or naphthyl): Anilines and naphthylamines form more stable diazonium salts, which can be isolated in the crystalline form. Diazonium salts undergo a variety of useful transformations involving replacement of the N group with anions. For example, cuprous cyanide gives the corresponding nitriles: Aryldiazonium couple with electron-rich aromatic compounds such as a phenol to form azo compounds. Such reactions are widely applied to the production of dyes. Imine formation is an important reaction. Primary amines react with ketones and aldehydes to form imines. In the case of formaldehyde (R′ H), these

neg: Period 2 element is liquid or gaseous—even at temperatures close to absolute zero. It is extremely difficult to isolate from any compounds, let alone keep uncombined. Fluorine gas is extremely dangerous material because it attacks almost all organic material, including live flesh. Many of the binary compounds that it forms (called fluorides) are themselves highly toxic, including soluble fluorides and especially hydrogen fluoride. But fluorine forms very strong bonds with many elements. With sulfur it can form the extremely stable and chemically inert sulfur hexafluoride; with carbon it can form the remarkable material Teflon that is a stable and non-combustible solid with a

neg: Calcium name derives from Latin "calx" "lime", which was obtained from heating limestone. Some calcium compounds were known to the ancients, though their chemistry was unknown until the seventeenth century. Pure calcium was isolated in 1808 via electrolysis of its oxide by Humphry Davy, who named the element. Calcium compounds are widely used in many industries: in foods and pharmaceuticals for calcium supplementation, in the paper industry as bleaches, as components in cement and electrical insulators, and in the manufacture of soaps. On the other hand, the metal in pure form has few applications due to its high reactivity; still, in

neg: Abandinus sings to (something/someone)’ or ‘(the god) who binds (something/someone) to (something/someone).’ However, it is also possible to see the name as an extended form of a variant form of the Proto-Celtic word *"abon"- ‘river,’ derived from the Proto-Indo-European root *"ab"-, *"h₂eb-" ‘water, river’. The Romano-Celtic name for the Humber is documented as having been "Abus" which suggests that a shorter element *"abo"- existed in the Proto-Celtic lexicon as a word for ‘river’ or ‘water.’ This *"abo"- element could have been the source of the "Ab-"- element in the theonym "Abandinus". So the name can also be analysed as *"Ab-Andinus" ‘Andinus

neg: -ane of an element. For instance, methane for CH and oxidane for HOwater. For the etymology of the term, see Alkane. <br> -ane The suffix -ane is used in organic chemistry to form names of organic compounds where the -C-C- group has been attributed the highest priority according to the rules of organic nomenclature. This type of Organic compounds are called as alkanes. They are saturated hydrocarbons. The hydrides of Silicon are called silanes SiH The hydrides of Boron are called boranes BH The names of the saturated hydrides of non-metals end with the suffix -ane The final "-e" disappears if

neg: Valence (chemistry) called bonds, representing a saturated valency for each element. The two tables below show some examples of different compounds, their valence diagrams, and the valences for each element of the compound. Valence only describes connectivity; it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. A line between atoms does not represent a pair of electrons as it does in Lewis diagrams. Valence is defined by the IUPAC as: An alternative modern description is: This definition differs from the IUPAC definition as an element can be said to

neg: Acrylic resin Acrylic resin Acrylic resins are a group of related thermoplastic or thermosetting plastic substances derived from acrylic acid, methacrylic acid or other related compounds. Polymethyl acrylate is an acrylic resin used in an emulsified form for lacquer, textile finishes, adhesives and, when mixed with clay, to gloss paper. Another acrylic resin is polymethyl methacrylate, which is used to make hard plastics with various light transmitting properties. It is used for the materials which need some light transmitting properties, because it is transparent as glass, some amount of titanium dioxide can be added for a translucent effect. The chemical name for

neg: Inorganic compounds by element Inorganic compounds by element This is a list of common inorganic and organometallic compounds of each element. Compounds are listed alphabetically by their chemical element name rather than by symbol, as in list of inorganic compounds. AcCl, AcF, AcO AlH, AlBr, AlBr, AlCl, AlCl(OH), AlF, AlGaAs, AlGaN, Al(OH), AlI, AlI, Al("i"-PrO), Al(NO), AlN, AlO, Al(SO), AlS, "i"-BuAlH (DIBAL-H), EtAlCl, LiAlH, (−Al(CH)O−), EtAl, MeAl AmCl, AmCl, AmF, AmO SbF, SbF, SbCl, SbCl, SbO, SbO, SbS, SbS, InSb, CHKOSb, KSbF, NaSbF, SbH, (CH)Sb HArF AsBr, AsCl, AsF, AsF, AsO, AsO, AsS, AsH, (CH)AsOOH, GaAs, KAsF, KHAsO, NaAsO, NaHAsO, NaAsO, (CH)As, (CH)As LiAt,

neg: Ytterbium Ytterbium Ytterbium is a chemical element with symbol Yb and atomic number 70. It is the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the other lanthanides, its most common oxidation state is +3, as in its oxide, halides, and other compounds. In aqueous solution, like compounds of other late lanthanides, soluble ytterbium compounds form complexes with nine water molecules. Because of its closed-shell electron configuration, its density and melting and boiling points differ significantly from those of most other lanthanides. In 1878, the Swiss

neg: Carbon-based life more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. For this reason, carbon has often been referred to as the "king of the elements". Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve

neg: Amidosulfite Amidosulfite An amidosulfite is a chemical compound containing the group =NS(O)O-. Substituents can attach two bonds to the nitrogen and one to the oxygen. These have the form RR'NS(O)OR" compounds can be a zwitterion with a positive charge on the nitrogen, and a negative charge on the oxygen, which then has no group attached. These can be called inner salts. This allows three groups to bond to the nitrogen: RR'R"NS(O)O. The simplest amidosulfite is amidosulfurous acid HNS(O)OH. It has ammonium salt HNS(O)ONH. These are purportedly produced when sulfur dioxide mixes with ammonia in ratios 1:1 or 1:2. Known compounds include

neg: Binary compounds of hydrogen the continuous phase of the solution is a metal, it is called a "metallic hydride" or "interstitial hydride", on account of the position of the hydrogen within the crystal structure of the metal. In solution, hydrogen can occur in either the atomic or molecular form. For some elements, when hydrogen content exceeds its solubility, the excess precipitates out as a stoichiometric compound. The table below shows the solubility of hydrogen in each element as a molar ratio at and 100 kPa. Binary compounds of hydrogen Binary compounds of hydrogen are binary chemical compounds containing just hydrogen and one other chemical

neg: Deoxygenation as oxides, so to produce elemental form of the element, deoxygenation is required. The main method involves carbothermic reduction (i.e., carbon is the deoxygenation agent). Oxophilic main group compounds are useful reagents for certain deoxygenations conducted on laboratory scale. The highly oxophilic reagent hexachlorodisilane (SiCl) stereospecifically deoxygenates phosphine oxides. A chemical reagent for the deoxygenation of many sulfur and nitrogen oxo compounds is the combination trifluoroacetic anhydride/sodium iodide. for example in the deoxygenation of the sulfoxide "diphenylsulfoxide" to the sulfide "diphenylsulfide": The reaction mechanism is based on activation of the sulfoxide by a trifluoroacetyl group and oxidation of iodine. Iodine

neg: 1,2,4-Trioxane 1,2,4-Trioxane 1,2,4-Trioxane is one of the isomers of trioxane. It has the molecular formula CHO and consists of a six membered ring with three carbon atoms and three oxygen atoms. The two adjacent oxygen atoms form a peroxide functional group and the other forms an ether functional group. It is like a cyclic acetal but with one of the oxygen atoms in the acetal group being replaced by a peroxide group. 1,2,4-Trioxane itself has not been isolated or characterized, but rather only studied computationally. However, it constitutes an important structural element of some more complex organic compounds. The natural compound

neg: A15 phases NMR spectrometers. A relaxed form of the Voronoi diagram of the A15 phase seems to have the least surface area among all the possible partitions of three-dimensional Euclidean space in regions of equal volume. This partition, also known as the Weaire–Phelan structure, is often present in clathrate hydrates. A15 phases The A15 phases (also known as β-W or CrSi structure types) are series of intermetallic compounds with the chemical formula "A""B" (where A is a transition metal and B can be any element) and a specific structure. Many of these compounds have superconductivity at around , which is comparatively high,

neg: Compounds of thorium a low-temperature superconductor. All three nitrides can react with thorium halides to form halide nitrides ThNX (X = F, Cl, Br, I). The heavier pnictogens also form analogous monopnictides, except ThBi which has not yet been structurally characterised. The other well-characterised thorium pnictides are ThP, ThP, ThP, ThAs, ThAs, ThSb, ThSb, and ThBi. Thorium reacts with hydrogen to form the thorium hydrides ThH and ThH, the latter of which is superconducting below the transition temperature of 7.5–8 K; at standard temperature and pressure, it conducts electricity like a metal. Thorium is the only element that forms a hydride higher than

neg: Group 12 element more clearly. For instance, zinc and cadmium are similar to beryllium and magnesium in their atomic radii, ionic radii, electronegativities, and also in the structure of their binary compounds and their ability to form complex ions with many nitrogen and oxygen ligands, such as complex hydrides and amines. However, beryllium and magnesium are small atoms, unlike the heavier alkaline earth metals and like the group 12 elements (which have a greater nuclear charge but the same number of valence electrons), and the periodic trends down group 2 from beryllium to radium (similar to that of the alkali metals) are not

neg: Chloride Chloride The chloride ion is the anion (negatively charged ion) Cl. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts such as sodium chloride are often very soluble in water. It is an essential electrolyte located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses and regulating fluid in and out of cells. Less frequently, the word "chloride" may also form part of the "common" name of chemical compounds in which one or more chlorine atoms

neg: Methylene group Methylene group In organic chemistry, a methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by a double bond. The group may be written =CH, where the '=' denotes the double bond. According to IUPAC, this structural element is named methylidene (name "methylene" should be used for −CH− group, also called “methylene bridge“). Many organic compounds are named and classified as if they were the result of substituting a methylene group for two adjacent hydrogen atoms of some parent molecule (even

neg: Apicophilicity Apicophilicity Apicophilicity is the phenomenon in which electronegative substituents of trigonal bipyramidal pentacoordinate compounds prefer to occupy apical positions (L). The term "apicophilicity" was first proposed by Earl L. Muetterties in 1963 for the structural analysis of pentacoordinate phosphorus fluorides by F NMR. Since the apical bonding of a pentacoordinate typical (group 1, 2, 13-18) element compound consists of a 3-center-4-electron bond, in which the electron density is localized on two apical substituents, an arrangement in which electronegative substituents occupy apical positions is more stable. The apicophilicity of a substituent is defined as the difference in energy between two isomeric

neg: Samarium explode, thus the heating rate has to be kept well below 1 °C/min. Similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at 1800 °C. Numerous crystalline binary compounds are known for samarium and one of the group-14, 15 or 16 element X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements. Many of the resulting compounds are non-stoichiometric and have nominal compositions SmX, where the b/a ratio varies between 0.5 and 3.

neg: Methylene bridge (dichloromethane ). However, the term methylene group (or "methylidene") properly applies to the group when it is connected to the rest of the molecule by a double bond, giving it chemical properties very distinct from those of a bridging group. Compounds possessing a methylene bridge located between two strong electron withdrawing groups (such as nitro, carbonyl or nitrile groups) are sometimes called active methylene compounds. Treatment of these with strong bases can form enolates or carbanions, which are often used in organic synthesis. Examples include the Knoevenagel condensation and the malonic ester synthesis. Some examples of methylene compounds are :

neg: Interchalcogen Interchalcogen The chalcogens react with each other to form interchalcogen compounds. Although no chalcogen is extremely electropositive, nor quite as electronegative as the halogen fluorine (the most electronegative element), there is a large difference in electronegativity between the top (oxygen = 3.44 — the second most electronegative element after fluorine) and bottom (polonium = 2.0) of the group. Combined with the fact that there is a significant trend towards increasing metallic behaviour while descending the group (oxygen is a gaseous nonmetal, while polonium is a silvery post-transition metal), this causes the interchalcogens to display many different kinds of bonding: covalent,

neg: Extraterrestrial life the unique ability to make four strong chemical bonds with other atoms, including other carbon atoms. These covalent bonds have a direction in space, so that carbon atoms can form the skeletons of complex 3-dimensional structures with definite architectures such as nucleic acids and proteins. Carbon forms more compounds than all other elements combined. The great versatility of the carbon atom makes it the element most likely to provide the bases—even exotic ones—for the chemical composition of life on other planets. Some bodies in the Solar System have the potential for an environment in which extraterrestrial life can exist, particularly

neg: IUPAC nomenclature of inorganic chemistry 2005 from IUPAC. Corrections have been issued. Apart from a reorganisation of the content, there is a new section on organometallics and a formal element list to be used in place of electronegativity lists in sequencing elements in formulae and names. The concept of a preferred IUPAC name (PIN), a part of the revised blue book for organic compound naming, has not yet been adopted for inorganic compounds. There are however guidelines as to which naming method should be adopted. The recommendations describe a number of different ways in which compounds can be named. These are: Additionally there are recommendations for

neg: Cycloalkane room for an additional numerical prefix if there is the need to include details of other attachments to the molecule such as chlorine or a methyl group. Another convention for the naming of compounds is the "common name", which is a shorter name and it gives less information about the compound. An example of a common name is terpineol, the name of which can tell us only that it is an alcohol (because the suffix "-ol" is in the name) and it should then have a hydroxy (–OH) group attached to it. An example of the IUPAC method is given

neg: Atom the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature and is the subject of the discipline of chemistry. The idea that matter is made up of discrete units is a very old

neg: Hilbert space self-adjoint operators and an imaginary multiple of a self adjoint operator that commute with each other. Normal operators can also usefully be thought of in terms of their real and imaginary parts. An element of is called unitary if is invertible and its inverse is given by . This can also be expressed by requiring that be onto and for all . The unitary operators form a group under composition, which is the isometry group of . An element of is compact if it sends bounded sets to relatively compact sets. Equivalently, a bounded operator is compact if, for any

neg: Isotopic labeling atoms in the products' structure to be determined. With information on the positioning of the isotopic atoms in the products, the reaction pathway the initial metabolites utilize to convert into the products can be determined. Radioactive isotopes can be tested using the autoradiographs of gels in gel electrophoresis. The radiation emitted by compounds containing the radioactive isotopes darkens a piece of photographic film, recording the position of the labeled compounds relative to one another in the gel. Isotope tracers are commonly used in the form of isotope ratios. By studying the ratio between two isotopes of the same element, we

neg: Friedrich Wöhler of ignorance, until 'one afternoon the miracle happened'". Nevertheless, it was the beginning of the end of one popular vitalist hypothesis, that of Jöns Jakob Berzelius, that "organic" compounds could be made only by living things. Wöhler was also known for being a co-discoverer of beryllium, silicon and silicon nitride, as well as the synthesis of calcium carbide, among others. In 1834, Wöhler and Justus Liebig published an investigation of the oil of bitter almonds. They proved by their experiments that a group of carbon, hydrogen, and oxygen atoms can behave like an element, take the place of an element,

neg: Explosive safer to handle; aluminium powder may be introduced to increase total energy and blast effects. Explosive compounds are also often "alloyed": HMX or RDX powders may be mixed (typically by melt-casting) with TNT to form Octol or Cyclotol. An oxidizer is a pure substance (molecule) that in a chemical reaction can contribute some atoms of one or more oxidizing elements, in which the fuel component of the explosive burns. On the simplest level, the oxidizer may itself be an oxidizing element, such as gaseous or liquid oxygen. The availability and cost of explosives are determined by the availability of the

neg: Vanadium the most common mode is beta decay. The electron capture reactions lead to the formation of element 22 (titanium) isotopes, while beta decay leads to element 24 (chromium) isotopes. The chemistry of vanadium is noteworthy for the accessibility of the four adjacent oxidation states 2–5. In aqueous solution, vanadium forms metal aquo complexes of which the colours are lilac [V(HO)], green [V(HO)], blue [VO(HO)], yellow VO. Vanadium(II) compounds are reducing agents, and vanadium(V) compounds are oxidizing agents. Vanadium(IV) compounds often exist as vanadyl derivatives, which contain the VO center. Ammonium vanadate(V) (NHVO) can be successively reduced with elemental zinc to