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A Criegee intermediate (also called a Criegee zwitterion or Criegee biradical) is a carbonyl oxide with two charge centers. These chemicals may react with sulfur dioxide and nitrogen oxides in the earth's atmosphere, and are implicated in the formation of aerosols, which are an important factor in controlling global climate. Criegee intermediates are also an important source of OH (hydroxyl radicals) | https://huggingface.co/datasets/fmars/wiki_stem |
Cross-conjugation is a special type of conjugation in a molecule, when in a set of three pi bonds only two pi bonds interact with each other by conjugation, while the third one is excluded from interaction. Whereas a normal conjugated system such as a polyene typically has alternating single and double bonds along consecutive atoms, a cross-conjugated system has an alkene unit bonded to one of the middle atoms of another conjugated chain through a single bond. In classical terms, one of the double-bonds branches off rather than continuing consecutively: the main chain is conjugated, and part of that same main chain is conjugated with the side group, but all parts are not conjugated together as strongly | https://huggingface.co/datasets/fmars/wiki_stem |
In molecular physics, crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually d or f orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). This theory has been used to describe various spectroscopies of transition metal coordination complexes, in particular optical spectra (colors). CFT successfully accounts for some magnetic properties, colors, hydration enthalpies, and spinel structures of transition metal complexes, but it does not attempt to describe bonding | https://huggingface.co/datasets/fmars/wiki_stem |
The cubical atom was an early atomic model in which electrons were positioned at the eight corners of a cube in a non-polar atom or molecule. This theory was developed in 1902 by Gilbert N. Lewis and published in 1916 in the article "The Atom and the Molecule" and used to account for the phenomenon of valency | https://huggingface.co/datasets/fmars/wiki_stem |
Cyclodipeptide synthases (CDPSs) are a newly defined family of peptide-bond forming enzymes that are responsible for the ribosome-independent biosynthesis of various cyclodipeptides, which are the precursors of many natural products with important biological activities. As a substrate for this synthesis, CDPSs use two amino acids activated as aminoacyl-tRNAs (aa-tRNAs), therefore diverting them from the ribosomal machinery. The first member of this family was identified in 2002 during the characterization of the albonoursin biosynthetic pathway in Streptomyces noursei | https://huggingface.co/datasets/fmars/wiki_stem |
The d-block contraction (sometimes called scandide contraction) is a term used in chemistry to describe the effect of having full d orbitals on the period 4 elements. The elements in question are gallium, germanium, arsenic, selenium, bromine, and krypton. Their electronic configurations include completely filled d orbitals (d10) | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond. The term delocalization is general and can have slightly different meanings in different fields:
In organic chemistry, it refers to resonance in conjugated systems and aromatic compounds.
In solid-state physics, it refers to free electrons that facilitate electrical conduction | https://huggingface.co/datasets/fmars/wiki_stem |
In coordination chemistry, denticity (from Latin dentis 'tooth') refers to the number of donor groups in a given ligand that bind to the central metal atom in a coordination complex. 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 | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a dihydrogen bond is a kind of hydrogen bond, an interaction between a metal hydride bond and an OH or NH group or other proton donor. With a van der Waals radius of 1. 2 Å, hydrogen atoms do not usually approach other hydrogen atoms closer than 2 | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry a donor number (DN) is a quantitative measure of Lewis basicity. A donor number is defined as the negative enthalpy value for the 1:1 adduct formation between a Lewis base and the standard Lewis acid SbCl5 (antimony pentachloride), in dilute solution in the noncoordinating solvent 1,2-dichloroethane with a zero DN. The units are kilocalories per mole for historical reasons | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist between two different elements: for example, in a carbonyl group between a carbon atom and an oxygen atom | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, the double bond rule states that elements with a principal quantum number (n) greater than 2 for their valence electrons (period 3 elements and higher) tend not to form multiple bonds (e. g. double bonds and triple bonds) | https://huggingface.co/datasets/fmars/wiki_stem |
Dunathan stereoelectronic hypothesis is a concept in chemistry to explain the stereospecefic cleavage of bonds using pyridoxal phosphate. This occurs because stereoelectronic effects controls the actions of the enzyme.
History
Before the correlation between fold type and reaction correlation of proteins were understood, Harmon C | https://huggingface.co/datasets/fmars/wiki_stem |
In atomic physics, the effective nuclear charge is the actual amount of positive (nuclear) charge experienced by an electron in a multi-electron atom. The term "effective" is used because the shielding effect of negatively charged electrons prevent higher energy electrons from experiencing the full nuclear charge of the nucleus due to the repelling effect of inner layer. The effective nuclear charge experienced by an electron is also called the core charge | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, the electromeric effect is a molecular polarization occurring by an intramolecular electron displacement characterized by the substitution of one electron pair for another within the same atomic octet of electrons. It is sometimes called the conjugative mechanism, and previously, the tautomeric mechanism). The electromeric effect is often considered along with the inductive effect as types of electron displacement | https://huggingface.co/datasets/fmars/wiki_stem |
The electron affinity (Eea) of an atom or molecule is defined as the amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion.
X(g) + e− → X−(g) + energyThis differs by sign from the energy change of electron capture ionization. The electron affinity is positive when energy is released on electron capture | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, electron counting is a formalism for assigning a number of valence electrons to individual atoms in a molecule. It is used for classifying compounds and for explaining or predicting their electronic structure and bonding. Many rules in chemistry rely on electron-counting:
Octet rule is used with Lewis structures for main group elements, especially the lighter ones such as carbon, nitrogen, and oxygen,
18-electron rule in inorganic chemistry and organometallic chemistry of transition metals,
Hückel's rule for the π-electrons of aromatic compounds,
Polyhedral skeletal electron pair theory for polyhedral cluster compounds, including transition metals and main group elements and mixtures thereof, such as boranes | https://huggingface.co/datasets/fmars/wiki_stem |
Electron deficiency (and electron-deficient) is jargon that is used in two contexts: species that violate the octet rule because they have too few valence electrons and species that happen to follow the octet rule but have electron-acceptor properties, forming donor-acceptor charge-transfer salts.
Octet rule violations
Traditionally, "electron-deficiency" is used as a general descriptor for boron hydrides and other molecules which do not have enough valence electrons to form localized (2-centre 2-electron) bonds joining all atoms. For example, diborane (B2H6) would require a minimum of 7 localized bonds with 14 electrons to join all 8 atoms, but there are only 12 valence electrons | https://huggingface.co/datasets/fmars/wiki_stem |
In quantum chemistry, the electron localization function (ELF) is a measure of the likelihood of finding an electron in the neighborhood space of a reference electron located at a given point and with the same spin. Physically, this measures the extent of spatial localization of the reference electron and provides a method for the mapping of electron pair probability in multielectronic systems.
ELF's usefulness stems from the observation that it allows electron localization to be analyzed in a chemically intuitive way | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, an electron pair or Lewis pair consists of two electrons that occupy the same molecular orbital but have opposite spins. Gilbert N. Lewis introduced the concepts of both the electron pair and the covalent bond in a landmark paper he published in 1916 | https://huggingface.co/datasets/fmars/wiki_stem |
Electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications:
with regards to electron-transfer, electron-rich species have low ionization energy and/or are reducing agents. Tetrakis(dimethylamino)ethylene is an electron-rich alkene because, unlike ethylene, it forms isolable radical cation. In contrast, electron-poor alkene tetracyanoethylene is an electron acceptor, forming isolable anions | https://huggingface.co/datasets/fmars/wiki_stem |
An electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications:
with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of the appended species. Tetracyanoethylene is an oxidant because the alkene is appended to four cyano substituents, which are electron-withdrawing.
with regards to acid-base reactions, acids with electron-withdrawing groups species have low acid dissociation constants | https://huggingface.co/datasets/fmars/wiki_stem |
Electronegativity, symbolized as χ, is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons | https://huggingface.co/datasets/fmars/wiki_stem |
Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electronegativities, and is the primary interaction occurring in ionic compounds. It is one of the main types of bonding, along with covalent bonding and metallic bonding. Ions are atoms (or groups of atoms) with an electrostatic charge | https://huggingface.co/datasets/fmars/wiki_stem |
In computational chemistry and computational physics, the embedded atom model, embedded-atom method or EAM, is an approximation describing the energy between atoms
and is a type of interatomic potential. The energy is a function of a sum of functions of the separation between an atom and its neighbors. In the original model, by Murray Daw and Mike Baskes, the latter functions represent the electron density | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a formal charge (F. C. or q*), in the covalent view of chemical bonding, is the hypothetical charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity | https://huggingface.co/datasets/fmars/wiki_stem |
A 4-center 2-electron (4c–2e) bond is a type of chemical bond in which four atoms share two electrons in bonding, with a net bond order of 1⁄2. This type of bonding differs from the usual covalent bond, which involves two atoms sharing two electrons (2c–2e bonding).
Four-center two-electron bonding is postulated in certain cluster compounds | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.
With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize | https://huggingface.co/datasets/fmars/wiki_stem |
The generalized valence bond (GVB) is a method in valence bond theory that uses flexible orbitals in the general way used by modern valence bond theory. The method was developed by the group of William A. Goddard, III around 1970 | https://huggingface.co/datasets/fmars/wiki_stem |
A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside | https://huggingface.co/datasets/fmars/wiki_stem |
A halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Like a hydrogen bond, the result is not a formal chemical bond, but rather a strong electrostatic attraction. Mathematically, the interaction can be decomposed in two terms: one describing an electrostatic, orbital-mixing charge-transfer and another describing electron-cloud dispersion | https://huggingface.co/datasets/fmars/wiki_stem |
The hydration number of a compound is defined as the number of molecules of water bonded to a central ion, often a metal cation. The hydration number is related to the broader concept of solvation number, the number of solvent molecules bonded to a central atom. The hydration number varies with the atom or ion of interest | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted Dn−H···Ac, where the solid line denotes a polar covalent bond, and the dotted or dashed line indicates the hydrogen bond. The most frequent donor and acceptor atoms are the period 2 elements nitrogen (N), oxygen (O), and fluorine (F) | https://huggingface.co/datasets/fmars/wiki_stem |
The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in an aqueous solution and exclude water molecules. The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes hydrogen bonding between molecules of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a hypervalent molecule (the phenomenon is sometimes colloquially known as expanded octet) is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells. Phosphorus pentachloride (PCl5), sulfur hexafluoride (SF6), chlorine trifluoride (ClF3), the chlorite (ClO−2) ion, and the triiodide (I−3) ion are examples of hypervalent molecules.
Definitions and nomenclature
Hypervalent molecules were first formally defined by Jeremy I | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, the inductive effect in a molecule is a local change in the electron density due to electron-withdrawing or electron-donating groups elsewhere in the molecule, resulting in a permanent dipole in a bond.
It is present in a σ (sigma) bond, unlike the electromeric effect which is present in a π (pi) bond.
The halogen atoms in an alkyl halide are electron withdrawing while the alkyl groups have electron donating tendencies | https://huggingface.co/datasets/fmars/wiki_stem |
The inert-pair effect is the tendency of the two electrons in the outermost atomic s-orbital to remain unshared in compounds of post-transition metals. The term inert-pair effect is often used in relation to the increasing stability of oxidation states that are two less than the group valency for the heavier elements of groups 13, 14, 15 and 16. The term "inert pair" was first proposed by Nevil Sidgwick in 1927 | https://huggingface.co/datasets/fmars/wiki_stem |
An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction
or repulsion which act between atoms and other types of neighbouring particles, e. g. atoms or ions | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, the intimate ion pair concept, introduced by Saul Winstein, describes the interactions between a cation, anion and surrounding solvent molecules. In ordinary aqueous solutions of inorganic salts, an ion is completely solvated and shielded from the counterion. In less polar solvents, two ions can still be connected to some extent | https://huggingface.co/datasets/fmars/wiki_stem |
An intramolecular force (or primary forces) is any force that binds together the atoms making up a molecule or compound, not to be confused with intermolecular forces, which are the forces present between molecules. The subtle difference in the name comes from the Latin roots of English with inter meaning between or among and intra meaning inside. Chemical bonds are considered to be intramolecular forces which are often stronger than intermolecular forces present between non-bonding atoms or molecules | https://huggingface.co/datasets/fmars/wiki_stem |
Inverted ligand field theory (ILFT) describes a phenomenon in the bonding of coordination complexes where the lowest unoccupied molecular orbital is primarily of ligand character. This is contrary to the traditional ligand field theory or crystal field theory picture and arises from the breaking down of the assumption that in organometallic complexes, ligands are more electronegative and have fronteir orbitals below those of the d orbitals of electropositive metals. As we move to the right of the d-block and approach the transition-metal - main group boundary, the d orbitals become more core-like, making their cations more electronegative | https://huggingface.co/datasets/fmars/wiki_stem |
Ioliomics (from a portmanteau of ions and liquids) is the study of ions in liquids (or liquid phases) and stipulated with fundamental differences of ionic interactions. Ioliomics covers a broad research area concerning structure, properties and applications of ions involved in various biological and chemical systems. The concept of this research discipline is related to other comprehensive research fields, such as genomics, proteomics, glycomics, petroleomics, etc | https://huggingface.co/datasets/fmars/wiki_stem |
An isopeptide bond is a type of amide bond formed between a carboxyl group of one amino acid and an amino group of another. An isopeptide bond is the linkage between the side chain amino or carboxyl group of one amino acid to the α-carboxyl, α-amino group, or the side chain of another amino acid. In a typical peptide bond, also known as eupeptide bond, the amide bond always forms between the α-carboxyl group of one amino acid and the α-amino group of the second amino acid | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, isovalent or second order hybridization is an extension of orbital hybridization, the mixing of atomic orbitals into hybrid orbitals which can form chemical bonds, to include fractional numbers of atomic orbitals of each type (s, p, d). It allows for a quantitative depiction of bond formation when the molecular geometry deviates from ideal bond angles.
Only bonding with 4 equivalent substituents results in exactly sp3 hybridization | https://huggingface.co/datasets/fmars/wiki_stem |
The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in spectroscopy, stereochemistry, crystal chemistry, molecular and solid-state physics, and materials science. The effect is named for Hermann Arthur Jahn and Edward Teller, who first reported studies about it in 1937. : sec | https://huggingface.co/datasets/fmars/wiki_stem |
Lewis structures{gjhxg{snd}}also called Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs) – are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule. A Lewis structure can be drawn for any covalently bonded molecule, as well as coordination compounds. The Lewis structure was named after Gilbert N | https://huggingface.co/datasets/fmars/wiki_stem |
In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs, often through Lewis bases. The nature of metal–ligand bonding can range from covalent to ionic | https://huggingface.co/datasets/fmars/wiki_stem |
Ligand bond number (LBN) represents the effective total number of ligands or ligand attachment points surrounding a metal center, labeled M. More simply, it represents the number of coordination sites occupied on the metal. Based on the covalent bond classification method (from where LBN is derived), the equation for determining ligand bond number is as follows:
LBN = L + X + ZWhere L represents the number of neutral ligands adding two electrons to the metal center (typically lone electron pairs, pi-bonds and sigma bonds | https://huggingface.co/datasets/fmars/wiki_stem |
Ligand field theory (LFT) describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes. A transition metal ion has nine valence atomic orbitals - consisting of five nd, one (n+1)s, and three (n+1)p orbitals | https://huggingface.co/datasets/fmars/wiki_stem |
A linear combination of atomic orbitals or LCAO is a quantum superposition of atomic orbitals and a technique for calculating molecular orbitals in quantum chemistry. In quantum mechanics, electron configurations of atoms are described as wavefunctions. In a mathematical sense, these wave functions are the basis set of functions, the basis functions, which describe the electrons of a given atom | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, linkage isomerism or ambidentate isomerism is a form of isomerism in which certain coordination compounds have the same composition but differ in their metal atom's connectivity to a ligand.
Typical ligands that give rise to linkage isomers are:
cyanide, CN− – isocyanide, NC−
cyanate, OCN− – isocyanate, NCO−
thiocyanate, SCN− – isothiocyanate, NCS−
selenocyanate, SeCN− – isoselenocyanate, NCSe−
nitrite, NO−2
sulfite, SO2−3Examples of linkage isomers are violet-colored [(NH3)5Co-SCN]2+ and orange-colored [(NH3)5Co-NCS]2+. The isomerization of the S-bonded isomer to the N-bonded isomer occurs intramolecularly | https://huggingface.co/datasets/fmars/wiki_stem |
A Low-barrier hydrogen bond (LBHB) is a special type of hydrogen bond. LBHBs can occur when the pKa of the two heteroatoms are closely matched, which allows the hydrogen to be more equally shared between them. This hydrogen-sharing causes the formation of especially short, strong hydrogen bonds | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, the mesomeric effect (or resonance effect) is a property of substituents or functional groups in a chemical compound. It is defined as the polarity produced in the molecule by the interaction of two pi bonds or between a pi bond and lone pair of electrons present on an adjacent atom. This change in electron arrangement results in the formation of resonance structures that hybridize into the molecule's true structure | https://huggingface.co/datasets/fmars/wiki_stem |
Metal aromaticity or metalloaromaticity is the concept of aromaticity, found in many organic compounds, extended to metals and metal-containing compounds. The first experimental evidence for the existence of aromaticity in metals was found in aluminium cluster compounds of the type MAl−4 where M stands for lithium, sodium or copper. These anions can be generated in a helium gas by laser vaporization of an aluminium / lithium carbonate composite or a copper or sodium / aluminium alloy, separated and selected by mass spectrometry and analyzed by photoelectron spectroscopy | https://huggingface.co/datasets/fmars/wiki_stem |
In organometallic chemistry, a metal–ligand multiple bond describes the interaction of certain ligands with a metal with a bond order greater than one. Coordination complexes featuring multiply bonded ligands are of both scholarly and practical interest. Transition metal carbene complexes catalyze the olefin metathesis reaction | https://huggingface.co/datasets/fmars/wiki_stem |
Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be described as the sharing of free electrons among a structure of positively charged ions (cations). Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and luster | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a metallophilic interaction is defined as a type of non-covalent attraction between heavy metal atoms. The atoms are often within Van der Waals distance of each other and are about as strong as hydrogen bonds. The effect can be intramolecular or intermolecular | https://huggingface.co/datasets/fmars/wiki_stem |
A molecular orbital diagram, or MO diagram, is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals (LCAO) method in particular. A fundamental principle of these theories is that as atoms bond to form molecules, a certain number of atomic orbitals combine to form the same number of molecular orbitals, although the electrons involved may be redistributed among the orbitals. This tool is very well suited for simple diatomic molecules such as dihydrogen, dioxygen, and carbon monoxide but becomes more complex when discussing even comparatively simple polyatomic molecules, such as methane | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, molecular orbital theory (MO theory or MOT) is a method for describing the electronic structure of molecules using quantum mechanics. It was proposed early in the 20th century.
In molecular orbital theory, electrons in a molecule are not assigned to individual chemical bonds between atoms, but are treated as moving under the influence of the atomic nuclei in the whole molecule | https://huggingface.co/datasets/fmars/wiki_stem |
The Morse potential, named after physicist Philip M. Morse, is a convenient
interatomic interaction model for the potential energy of a diatomic molecule. It is a better approximation for the vibrational structure of the molecule than the quantum harmonic oscillator because it explicitly includes the effects of bond breaking, such as the existence of unbound states | https://huggingface.co/datasets/fmars/wiki_stem |
Multi-state modeling of biomolecules refers to a series of techniques used to represent and compute the behaviour of biological molecules or complexes that can adopt a large number of possible functional states.
Biological signaling systems often rely on complexes of biological macromolecules that can undergo several functionally significant modifications that are mutually compatible. Thus, they can exist in a very large number of functionally different states | https://huggingface.co/datasets/fmars/wiki_stem |
Nascent state or in statu nascendi (Lat. newly formed moiety: in the state of being born or just emerging), is an obsolete theory in chemistry. It refers to the form of a chemical element (or sometimes compound) in the instance of their liberation or formation | https://huggingface.co/datasets/fmars/wiki_stem |
A network solid or covalent network solid (also called atomic crystalline solids or giant covalent structures) is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal or amorphous solid may be considered a macromolecule. Formulas for network solids, like those for ionic compounds, are simple ratios of the component atoms represented by a formula unit | https://huggingface.co/datasets/fmars/wiki_stem |
A non-bonding orbital, also known as non-bonding molecular orbital (NBMO), is a molecular orbital whose occupation by electrons neither increases nor decreases the bond order between the involved atoms. Non-bonding orbitals are often designated by the letter n in molecular orbital diagrams and electron transition notations. Non-bonding orbitals are the equivalent in molecular orbital theory of the lone pairs in Lewis structures | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a non-covalent interaction differs from a covalent bond in that it does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule. The chemical energy released in the formation of non-covalent interactions is typically on the order of 1–5 kcal/mol (1000–5000 calories per 6. 02×1023 molecules) | https://huggingface.co/datasets/fmars/wiki_stem |
The Non-Covalent Interactions index, commonly referred to as simply Non-Covalent Interactions (NCI) is a visualization index based in the Electron density (ρ) and the reduced density gradient (s). It is based on the empirical observation that Non-covalent interactions can be associated with the regions of small reduced density gradient at low electronic densities. In quantum chemistry, the non-covalent interactions index is used to visualize non-covalent interactions in three-dimensional space | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, a (redox) non-innocent ligand is a ligand in a metal complex where the oxidation state is not
clear. Typically, complexes containing non-innocent ligands are redox active at mild potentials. The concept assumes that redox reactions in metal complexes are either metal or ligand localized, which is a simplification, albeit a useful one | https://huggingface.co/datasets/fmars/wiki_stem |
In chemical bonds, an orbital overlap is the concentration of orbitals on adjacent atoms in the same regions of space. Orbital overlap can lead to bond formation. Linus Pauling explained the importance of orbital overlap in the molecular bond angles observed through experimentation; it is the basis for orbital hybridization | https://huggingface.co/datasets/fmars/wiki_stem |
In quantum mechanics, the Pauli exclusion principle states that two or more identical particles with half-integer spins (i. e. fermions) cannot occupy the same quantum state within a quantum system simultaneously | https://huggingface.co/datasets/fmars/wiki_stem |
Pauling's principle of electroneutrality states that each atom in a stable substance has a charge close to zero. It was formulated by Linus Pauling in 1948 and later revised. The principle has been used to predict which of a set of molecular resonance structures would be the most significant, to explain the stability of inorganic complexes and to explain the existence of π-bonding in compounds and polyatomic anions containing silicon, phosphorus or sulfur bonded to oxygen; it is still invoked in the context of coordination complexes | https://huggingface.co/datasets/fmars/wiki_stem |
In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein chain. It can also be called a eupeptide bond to distinguish it from an isopeptide bond, which is another type of amide bond between two amino acids.
Synthesis
When two amino acids form a dipeptide through a peptide bond, it is a type of condensation reaction | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, π backbonding, also called π backdonation, is when electrons move from an atomic orbital on one atom to an appropriate symmetry antibonding orbital on a π-acceptor ligand. It is especially common in the organometallic chemistry of transition metals with multi-atomic ligands such as carbon monoxide, ethylene or the nitrosonium cation. Electrons from the metal are used to bond to the ligand, in the process relieving the metal of excess negative charge | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end.
Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. Molecules containing polar bonds have no molecular polarity if the bond dipoles cancel each other out by symmetry | https://huggingface.co/datasets/fmars/wiki_stem |
In chemistry the polyhedral skeletal electron pair theory (PSEPT) provides electron counting rules useful for predicting the structures of clusters such as borane and carborane clusters. The electron counting rules were originally formulated by Kenneth Wade, and were further developed by others including Michael Mingos; they are sometimes known as Wade's rules or the Wade–Mingos rules. The rules are based on a molecular orbital treatment of the bonding | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a compressed suffix array is a compressed data structure for pattern matching. Compressed suffix arrays are a general class of data structure that improve on the suffix array. These data structures enable quick search for an arbitrary string with a comparatively small index | https://huggingface.co/datasets/fmars/wiki_stem |
Document retrieval is defined as the matching of some stated user query against a set of free-text records. These records could be any type of mainly unstructured text, such as newspaper articles, real estate records or paragraphs in a manual. User queries can range from multi-sentence full descriptions of an information need to a few words | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, an FM-index is a compressed full-text substring index based on the Burrows–Wheeler transform, with some similarities to the suffix array. It was created by Paolo Ferragina and Giovanni Manzini, who describe it as an opportunistic data structure as it allows compression of the input text while still permitting fast substring queries. The name stands for Full-text index in Minute space | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a generalized suffix array (or GSA) is a suffix array containing all suffixes for a set of strings. Given the set of strings
S
=
S
1
,
S
2
,
S
3
,
.
| https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a generalized suffix tree is a suffix tree for a set of strings. Given the set of strings
D
=
S
1
,
S
2
,
…
,
S
d
{\displaystyle D=S_{1},S_{2},\dots ,S_{d}}
of total length
n
{\displaystyle n}
, it is a Patricia tree containing all
n
{\displaystyle n}
suffixes of the strings. It is mostly used in bioinformatics | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, an inverted index (also referred to as a postings list, postings file, or inverted file) is a database index storing a mapping from content, such as words or numbers, to its locations in a table, or in a document or a set of documents (named in contrast to a forward index, which maps from documents to content). The purpose of an inverted index is to allow fast full-text searches, at a cost of increased processing when a document is added to the database. The inverted file may be the database file itself, rather than its index | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, the longest common prefix array (LCP array) is an auxiliary data structure to the suffix array. It stores the lengths of the longest common prefixes (LCPs) between all pairs of consecutive suffixes in a sorted suffix array.
For example, if A := [aab, ab, abaab, b, baab] is a suffix array, the longest common prefix between A[1] = aab and A[2] = ab is a which has length 1, so H[2] = 1 in the LCP array H | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a suffix array is a sorted array of all suffixes of a string. It is a data structure used in, among others, full-text indices, data-compression algorithms, and the field of bibliometrics.
Suffix arrays were introduced by Manber & Myers (1990) as a simple, space efficient alternative to suffix trees | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a suffix tree (also called PAT tree or, in an earlier form, position tree) is a compressed trie containing all the suffixes of the given text as their keys and positions in the text as their values. Suffix trees allow particularly fast implementations of many important string operations.
The construction of such a tree for the string
S
{\displaystyle S}
takes time and space linear in the length of
S
{\displaystyle S}
| https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, a 2–3 heap is a data structure, a variation on the heap, designed by Tadao Takaoka in 1999. The structure is similar to the Fibonacci heap, and borrows from the 2–3 tree.
Time costs for some common heap operations are:
Delete-min takes
O
(
log
(
n
)
)
{\displaystyle O(\log(n))}
amortized time | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, an (a,b) tree is a kind of balanced search tree.
An (a,b)-tree has all of its leaves at the same depth, and all internal nodes except for the root have between a and b children, where a and b are integers such that 2 ≤ a ≤ (b+1)/2. The root has, if it is not a leaf, between 2 and b children | https://huggingface.co/datasets/fmars/wiki_stem |
An adaptive k-d tree is a tree for multidimensional points where successive levels may be split along different dimensions.
References
This article incorporates public domain material from Paul E. Black | https://huggingface.co/datasets/fmars/wiki_stem |
In computational number theory, the Adleman–Pomerance–Rumely primality test is an algorithm for determining whether a number is prime. Unlike other, more efficient algorithms for this purpose, it avoids the use of random numbers, so it is a deterministic primality test. It is named after its discoverers, Leonard Adleman, Carl Pomerance, and Robert Rumely | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, the AF-heap is a type of priority queue for integer data, an extension of the fusion tree using an atomic heap proposed by M. L. Fredman and D | https://huggingface.co/datasets/fmars/wiki_stem |
The Algorithm BSTW is a data compression algorithm, named after its designers, Bentley, Sleator, Tarjan and Wei in 1986. BSTW is a dictionary-based algorithm that uses a move-to-front transform to keep recently seen dictionary entries at the front of the dictionary. Dictionary references are then encoded using any of a number of encoding methods, usually Elias delta coding or Elias gamma coding | https://huggingface.co/datasets/fmars/wiki_stem |
A BANG file[1](balanced and nested grid file) is a point access method which divides space into a nonperiodic grid. Each spatial dimension is divided by a linear hash. Cells may intersect, and points may be distributed between them | https://huggingface.co/datasets/fmars/wiki_stem |
The BCJR algorithm is an algorithm for maximum a posteriori decoding of error correcting codes defined on trellises (principally convolutional codes). The algorithm is named after its inventors: Bahl, Cocke, Jelinek and Raviv. This algorithm is critical to modern iteratively-decoded error-correcting codes, including turbo codes and low-density parity-check codes | https://huggingface.co/datasets/fmars/wiki_stem |
Image morphing is a technique to synthesize a fluid transformation from one image (source image) to another (destination image). Source image can be one or more than one images. There are two parts in the image morphing implementation | https://huggingface.co/datasets/fmars/wiki_stem |
In mathematics, in particular in computational algebra, the Berlekamp–Zassenhaus algorithm is an algorithm for factoring polynomials over the integers, named after Elwyn Berlekamp and Hans Zassenhaus. As a consequence of Gauss's lemma, this amounts to solving the problem also over the rationals.
The algorithm starts by finding factorizations over suitable finite fields using Hensel's lemma to lift the solution from modulo a prime p to a convenient power of p | https://huggingface.co/datasets/fmars/wiki_stem |
Best bin first is a search algorithm that is designed to efficiently find an approximate solution to the nearest neighbor search problem in very-high-dimensional spaces. The algorithm is based on a variant of the kd-tree search algorithm which makes indexing higher-dimensional spaces possible. Best bin first is an approximate algorithm which returns the nearest neighbor for a large fraction of queries and a very close neighbor otherwise | https://huggingface.co/datasets/fmars/wiki_stem |
The brain storm optimization algorithm is a heuristic algorithm that focuses on solving multi-modal problems, such as radio antennas design worked on by Yahya Rahmat-Samii, inspired by the brainstorming process, proposed by Dr. Yuhui Shi. More than 200 papers related to BSO algorithms have appeared in various journals and conferences | https://huggingface.co/datasets/fmars/wiki_stem |
In computer science, the Brodal queue is a heap/priority queue structure with very low worst case time bounds:
O
(
1
)
{\displaystyle O(1)}
for insertion, find-minimum, meld (merge two queues) and decrease-key and
O
(
l
o
g
(
n
)
)
{\displaystyle O(\mathrm {log} (n))}
for delete-minimum and general deletion. They are the first heap variant to achieve these bounds without resorting to amortization of operational costs. Brodal queues are named after their inventor Gerth Stølting Brodal | https://huggingface.co/datasets/fmars/wiki_stem |
A C-trie is a compressed trie data structure. It achieves lower memory and query time requirements at the expense of reduced flexibility.
References
Maly, K | https://huggingface.co/datasets/fmars/wiki_stem |
Chaitin's algorithm is a bottom-up, graph coloring register allocation algorithm that uses cost/degree as its spill metric. It is named after its designer, Gregory Chaitin. Chaitin's algorithm was the first register allocation algorithm that made use of coloring of the interference graph for both register allocations and spilling | https://huggingface.co/datasets/fmars/wiki_stem |
In computational geometry, a constrained Delaunay triangulation is a generalization of the Delaunay triangulation that forces certain required segments into the triangulation as edges, unlike the Delaunay triangulation itself which is based purely on the position of a given set of vertices without regard to how they should be connected by edges. It can be computed efficiently and has applications in geographic information systems and in mesh generation.
Definition
The input to the constrained Delaunay triangulation problem is a planar straight-line graph, a set of points and non-crossing line segments in the plane | https://huggingface.co/datasets/fmars/wiki_stem |
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