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Coordination Number
In chemistry, crystallography, and materials science the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals. For molecules and polyatomic ions the coordination number of an atom is determined by simply counting the other atoms to which it is bonded (by either single or multiple bonds).[1] For example, [Cr(NH3)2Cl2Br2]− has Cr3+ as its central cation, and has a coordination number of 6. However the solid-state structures of crystals often have less clearly defined bonds, and in these cases a count of neighboring atoms is employed. The simplest method is one used in materials science. The usual value of the coordination number for a given structure refers to an atom in the interior of a crystal lattice with neighbors in all directions
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Caesium Chloride
Caesium
Caesium
chloride or cesium chloride is the inorganic compound with the formula CsCl. This colorless solid is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chlorine ions. Caesium
Caesium
chloride dissolves in water. Caesium
Caesium
chloride occurs naturally as impurities in carnallite (up to 0.002%), sylvite and kainite. Less than 20 tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral pollucite.[7] Caesium
Caesium
chloride is widely used medicine structure in isopycnic centrifugation for separating various types of DNA. It is a reagent in analytical chemistry, where it is used to identify ions by the color and morphology of the precipitate
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Hapticity
Hapticity
Hapticity
is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms.[1] The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated (otherwise the κ-notation is used). In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity [2] (not hapticity), and the κ-notation is used once again.[3] When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.[4][5]Contents1 History1.1 Historically important compounds where the ligands are described with hapticity2 Examples2.1 Electrons donated by "π- ligands" vs. hapticity3 Changes in hapticity 4 Hapticity
Hapticity
vs
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Bidentate
Denticity
Denticity
refers to the number of donor groups in a single ligand that bind to a central atom in a coordination complex.[1][2] In many cases, only one atom in the ligand binds to the metal, so the denticity equals one, and the ligand is said to be monodentate (sometimes called unidentate). Ligands with more than one bonded atom are called polydentate or multidentate. The word denticity is derived from dentis, the Latin word for tooth. The ligand is thought of as biting the metal at one or more linkage points. The denticity of a ligand is described with the Greek letter κ ('kappa').[3] For example, κ6-EDTA describes an EDTA
EDTA
ligand that coordinates through 6 non-contiguous atoms. Denticity
Denticity
is different from hapticity because hapticity refers exclusively to ligands where the coordinating atoms are contiguous
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Nitrate
Nitrate
Nitrate
is a polyatomic ion with the molecular formula NO− 3 and a molecular mass of 62.0049 u. Nitrates also describe the organic functional group RONO2. These nitrate esters are a specialized class of explosives.Contents1 Structure 2 Properties and diet 3 Occurrence 4 Uses 5 Detection 6 Toxicity6.1 Poisoning 6.2 Human health effects 6.3 Marine toxicity7 Nitrate
Nitrate
overview 8 See also 9 References 10 External linksStructure[edit] The anion is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of −1. This results from a combination formal charge in which each of the three oxygens carries a −​2⁄3 charge, whereas the nitrogen carries a +1 charge, all these adding up to formal charge of the polyatomic nitrate ion
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Computational Chemistry
Computational chemistry
Computational chemistry
is a branch of chemistry that uses computer simulation to assist in solving chemical problems. It uses methods of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids. It is necessary because, apart from relatively recent results concerning the hydrogen molecular ion (dihydrogen cation, see references therein for more details), the quantum many-body problem cannot be solved analytically, much less in closed form
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Lead
Lead
Lead
is a chemical element with symbol Pb (from the Latin
Latin
plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead
Lead
is soft and malleable, and has a relatively low melting point. When freshly cut, lead is bluish-white; it tarnishes to a dull gray color when exposed to air. Lead
Lead
has the highest atomic number of any stable element and three of its isotopes each conclude a major decay chain of heavier elements. Lead
Lead
is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead
Compounds of lead
are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group
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Terphenyl
Terphenyls are a group of closely related aromatic hydrocarbons. Also known as diphenylbenzenes or triphenyls, they consist of a central benzene ring substituted with two phenyl groups. The three isomers are ortho-terphenyl, meta-terphenyl, and para-terphenyl. Commercial grade terphenyl is generally a mixture of the three isomers. This mixture is used in the production of polychlorinated terphenyls, which were formerly used as heat storage and transfer agents.[2] p-Terphenyl is the most common isomer. It is used as a laser dye and a sunscreen ingredient.[2]ortho-Terphenylmeta-Terphenylpara-TerphenylSee also[edit]Biphenyl Terpyridine TerthiopheneReferences[edit]^ a b c Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 345
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Cyclopentadienide
Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp, where Cp− is the cyclopentadienide anion.[1] Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.[2] Preparation[edit] Sodium cyclopentadienide is commercially available as a solution in THF. It is prepared by treating cyclopentadiene with sodium:[3]2 Na + 2 C5H6 → 2 NaC5H5 + H2Commonly, the conversion is conducted by heating a suspension of molten sodium in dicyclopentadiene.[2] In former times, the sodium was commonly provided in the form of "sodium wire" or "sodium sand", a fine dispersion of sodium prepared by melting sodium in refluxing xylene and rapidly stirring.[4][5] Sodium hydride is a convenient base:[6]NaH + C5H6 → NaC5H5 + H2In early work, Grignard reagents were used as bases
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Alkene
In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond.[1] The words alkene and olefin are often used interchangeably (see nomenclature section below). Acyclic alkenes, with only one double bond and no other functional groups, known as mono-enes, form a homologous series of hydrocarbons with the general formula CnH2n.[2] Alkenes have two hydrogen atoms fewer than the corresponding alkane (with the same number of carbon atoms)
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Cyclooctatetraenide
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy. Unlike benzene, C6H6, cyclooctatetraene, C8H8, is not aromatic, although its dianion, C 8H2− 8 (cyclooctatetraenide), is. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions
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Ferrocene
[3]NFPA 7043US health exposure limits (NIOSH):PEL (Permissible)TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)[5]REL (Recommended)TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)[5] IDLH
IDLH
(Immediate danger)N.D.[5]Related compoundsRelated compoundscobaltocene, nickelocene, chromocene, ruthenocene, osmocene, plumboceneExcept where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).N verify (what is YN ?)Infobox references Ferrocene
Ferrocene
is an organometallic compound with the formula Fe(C5H5)2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom
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Metal Carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel carbonyl is used to produce pure nickel
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X-ray Crystallography
X-ray
X-ray
crystallography is a technique used for determining the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays
X-rays
to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules— X-ray
X-ray
crystallography has been fundamental in the development of many scientific fields
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Neutron Diffraction
Neutron
Neutron
diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of the structure of the material
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Electron Diffraction
Electron
Electron
diffraction refers to the wave nature of electrons. However, from a technical or practical point of view, it may be regarded as a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern. This phenomenon is commonly known as wave–particle duality, which states that a particle of matter (in this case the incident electron) can be described as a wave. For this reason, an electron can be regarded as a wave much like sound or water waves. This technique is similar to X-ray
X-ray
and neutron diffraction. Electron
Electron
diffraction is most frequently used in solid state physics and chemistry to study the crystal structure of solids. Experiments are usually performed in a transmission electron microscope (TEM), or a scanning electron microscope (SEM) as electron backscatter diffraction
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