negative charge than the hydrogen atoms of a water molecule . Electronegativity , symbol the Greek ... E01990 title Electronegativity ref An atom s electronegativity is affected by both its atomic number ... electronegativity number, the more an element or compound attracts electrons towards it. First ... of Single Bonds and the Relative Electronegativity of Atoms doi 10.1021 ja01348a011 ref it has been shown to correlate with a number of other chemical properties. Electronegativity cannot be directly ... have been proposed, and although there may be small differences in the numerical values of the electronegativity ... values this is known as an electronegativity in Pauling units . Electronegativity, as it is usually ... ionization energy and electron affinity . It is to be expected that the electronegativity of an element ... values will be valid in a variety of situations. On the most basic level, electronegativity is determined ... will act to shield the valence electrons from the positively charged nucleus . The opposite of electronegativity ... decreases Ionization energy increases Electronegativity increases Periodic table group Group vertical ... table of electronegativity using the Pauling scale See also Electronegativities of the elements data page . center Methods of calculation Pauling electronegativity Linus Pauling Pauling first proposed ref name paulingJACS the concept of electronegativity in 1932 as an explanation of the fact that the covalent ... of ionic canonical form s to the bonding. The difference in electronegativity between atoms ... result. Hence, the difference in Pauling electronegativity between hydrogen and bromine is 0.73 dissociation energies H Br, 3.79 eV H H, 4.52 eV Br Br 2.00 eV As only differences in electronegativity ... of elements its electronegativity was fixed first ref name paulingJACS at 2.1, later revised ref ... volume 17 issue 3 4 pages 215 221 title Electronegativity values from thermochemical data doi .... To calculate Pauling electronegativity for an element, it is necessary to have data on the dissociation ... more details
wiktionary Negativity may refer to Negative charge of electricity Electronegativity , a chemical property pertaining to the ability to attract electrons Positivity negativity ratio , in behavioral feedback Negativity effect , a psychological bias See also Negative disambiguation Negativism disambiguation disambiguation ... more details
Image Van Arkel Ketelaar triangle.svg thumb 200px right A Van Arkel Ketelaar triangle Bond triangles or van Arkel Ketelaar triangles named after Anton Eduard van Arkel and J. A. A. Ketelaar are triangles used to show different compounds in varying degrees of ionic bond ionic , metallic bond metallic and covalent bonding . The bond triangle shows that ionic, metallic and covalent bonds are not just particular bonds of a specific type. Rather, bond types are interconnected and different compounds have varying degrees of different bonding character for example, covalent bonds with significant ionic character are called polar covalent bonds . Different compounds can be placed around the triangle. On the right side from ionic to covalent should be compounds with varying difference in electronegativity , in the covalent corner compounds with equal electronegativity such as Cl sub 2 sub chlorine , in the ionic corner compounds with large electronegativity difference such as Sodium chloride NaCl table salt . The bottom side from metallic to covalent is for compounds with varying degree of directionality in the bond. At one extreme is metallic bonds with delocalized bonding and the other are covalent bonds in which the orbitals overlap in a particular direction. The left side from ionic to metallic is for delocalized bonds with varying electronegativity difference. Three species at the vertices of the triangle are caesium metallic , fluorine covalent and caesium fluoride ionic . External links http www.meta synthesis.com webbook 37 ak triangles.html Van Arkel Ketelaar Triangles of Bonding Category Chemical bonding ar es Tri ngulo de Van Arkel Ketelaar ... more details
, the electron affinity will increase. Electronegativity Main ElectronegativityElectronegativity ... bond. The type of bond formed is largely determined by the difference in electronegativity ... across a period in the periodic table, the electronegativity increases due to the stronger attraction that the atoms obtain as the nuclear charge increases. Moving down a group, the electronegativity ... 13 elements electronegativity increases from Aluminium to Thallium . In group 14 electronegativity ... more details
In chemistry , a polar bond is a type of covalent bond between two atoms or more in which electrons are shared unequally. Because of this, one end of the molecule has a slight, relative negative charge and the other a slight, relative positive charge. An example of atoms bonded by a polar bond is the water molecule , which is made up of two hydrogen atoms and one oxygen atom. Chemical polarity Covalent bond Bond dipole moment Partial charge Dipoles Molecular dipoles Molecular dipole Electronegativity Category Chemical bonding simple Polar bond uk ... more details
This page is about transferability in chemistry. Transferability in economics also exists. Transferability , in chemistry , is the assumption that a chemical property that is associated with an atom or a functional group in a molecule will have a similar but not identical value in a variety of different circumstances. ref http goldbook.iupac.org T06441.html Transferability . Compendium of Chemical Terminology . ref Examples of transferable properties include Electronegativity Nucleophilicity Chemical shifts in NMR spectroscopy Characteristic frequencies in Infrared spectroscopy Transferable properties are distinguished from conserved properties , which are assumed to always have the same value whatever the chemical situation, e.g. relative atomic mass . References references chemistry stub Category Chemical properties ja ... more details
Orphan date February 2009 A metaoxyacid is an acid related to oxoacid . Like oxoacids, metaoxyacids share a few similarities. ref Chemistry of the Carbon Compounds Or, Organic Chemistry. Victor von Richter.Blakiston. http books.google.com books?id qxNDAAAAIAAJ ref Specifically they contains oxygen contains at least one other Chemical element element has at least one hydrogen atom bound to oxygen and forms an ion by the loss of one or more protons. However, they are distinguished in that metaoxyacids have a distinct, differing molecular structure from all oxoacids dissolve in a dissimilar manner are more stable and do not disperse in aqueous solutions Generally, oxoacids are simply polyatomic ions with a hydrogen cation , and a metaoxyacid is similar but less reactive. See also Strong Acid Weak Acid Electronegativity References reflist Category Acids chem stub ... more details
saved book title Chemistry subtitle cover image Chemicals in flasks.jpg cover color Black Chemistry Overview Alchemy Chemistry History of chemistry Alchemy and chemistry in medieval Islam Timeline of chemistry Atoms and molecules Atom Atomic nucleus Proton Neutron Electron Chemical element Isotope Ion Molecule Chemical compound Chemical substance Common phases of matter Phase matter Phases Gas Liquid Solid Periodic table Valence electron Periodic table Periodic trends Period periodic table Period Group periodic table Group Chemical concepts Ionic radius Effective nuclear charge Electronegativity Mole unit Mole Lewis structure Chemical bond Chemical reactions Chemical reaction Chemical law Solution Acid Redox Reduction oxidation Miscellaneous Chemistry etymology Etymology Chemical industry Category Wikipedia books on chemistry ... more details
The Hume Rothery rules , named after William Hume Rothery , are a set of basic rules describing the conditions under which an element could dissolve in a metal , forming a solid solution . There are two sets of rules, one which refers to substitutional solid solutions, and another which refers to Interstitial defect interstitial solid solutions. Substitutional Solid Solution Rules For substitutional solid solutions, the Hume Rothery rules are 1. The Atomic radius atomic radii of the solute and solvent atoms must differ by no more than 15 math mbox difference left frac r solute r solvent r solvent right 100 le 15 . math 2. The crystal structure s of solute and solvent must match. 3. Complete solubility occurs when the solvent and solute have the same Valence chemistry valency . ref Foundations of Materials Science and Engineering , 4th ed., W. Smith and J. Hashemi, pp.139 140 2006 . ref A metal will dissolve a metal of higher valency to a greater extent than one of lower valency. 4. The solute and solvent should have similar electronegativity . If the electronegativity difference is too great, the metals will tend to form Intermetallics intermetallic compounds instead of solid solutions. Interstitial Solid Solution Rules For Interstitial defect interstitial solid solutions, the Hume Rothery rules are 1. Solute atoms must be smaller than the interstitial sites in the solvent lattice. 2. The solute and solvent should have similar electronegativity . ref cite encyclopedia title Hume Rothery Rules encyclopedia Van Nostrand s Scientific Encyclopedia publisher John Wiley & Sons, Inc year 2002 ref Notes reflist References cite web last Bhadeshia first H. K. D. H. title Solid Solutions The Hume Rothery Rules url http www.msm.cam.ac.uk phase trans 2004 titanium hume.rothery.html accessdate 2007 11 24 Further reading Cite book last Mizutani first Uichiro title Hume Rothery Rules for Structurally Complex Alloy Phases publisher Taylor & Francis date 2010 isbn 9781420090581 DEFAU ... more details
, or 73 pm. This value, however, is inaccurate due to the large electronegativity and small radius ... together. Ronald Gillespie File Bond length of fluorine graph.JPG thumb 300px right By plotting electronegativity ... against the electronegativity see figure . From this, they discovered that the Schomaker Stevenson ... more details
electronegativity and measures the attraction for electrons a particular atom has. The unequal ... atoms, as electrons will be drawn closer to the atom with the higher electronegativity. Bonds ... bond using numerical means, the difference between the electronegativity of the atoms is taken. If the result ... atoms. A molecule may be polar either as a result of polar bonds due to differences in electronegativity ... there is no electronegativity difference between atoms of the same element . However, the distribution ... polarity in the covalent bond because of equal electronegativity, hence there is no polarity in the molecule ... bond Electronegativity Dielectric Chemical bonding References Reflist refimprove date December ... more details
In chemistry , heterolysis or heterolytic fission from Greek , heteros, different, and , lusis, loosening is chemical bond cleavage of a neutral molecule generating a cation and an anion . ref GoldBookRef title heterolysis heterolytic file H02809 ref In this process the two electron s that make up the bond are assigned to the same fragment. The more Electronegativity electronegative fragment receives both electrons. File Heterolysis Chemistry .png 350px The energy involved in this process is called heterolytic bond dissociation energy. Bond cleavage is also possible by a process called homolysis . In heterolysis additional energy is required to separate the ion pair. An ionising solvent helps reduce this energy. In biology , heterolysis refers to apoptosis induced by hydrolytic enzymes from surrounding usually inflammatory cells. Autolysis is apoptosis of a cell by its own enzymes. See also Homolysis References Reflist chemistry stub Category Chemical reactions ar ca Heter lisi cs Heterol za cy Heterolysis de Heterolytische Spaltung et Heterol s es Heter lisis fr H t rolyse he nl Heterolytische splitsing ja pl Heterolityczny rozpad wi zania sh Heteroliza ... more details
Chembox ImageFile Benzoylthiomethylecgonine.svg ImageSize 250px ImageAlt IUPACName OtherNames Section1 Chembox Identifiers CASNo 287488 21 5 CASNo Ref cascite correct PubChem SMILES Section2 Chembox Properties C 17 H 21 N 1 O 3 S 1 Appearance Density MeltingPt BoilingPt Solubility Section3 Chembox Hazards MainHazards FlashPt Autoignition Benzoylthiomethylecgonine is a List of cocaine analogues cocaine analog which includes a sulfur in replacement of an oxygen on the single bonded benzoyl ester, resulting in lower electronegativity than the parent compound. ref cite journal doi 10.1021 ja012376y title Synthesis, Properties, and Reactivity of Cocaine Benzoylthio Ester Possessing the Cocaine Absolute Configuration year 2002 last1 Isomura first1 Shigeki last2 Hoffman first2 Timothy Z. last3 Wirsching first3 Peter last4 Janda first4 Kim D. journal Journal of the American Chemical Society volume 124 issue 14 pages 3661 8 pmid 11929256 ref See also Salicylmethylecgonine 2 Acetoxycocaine 4 Fluorococaine References references stimulants Category Tropanes Category Dopamine reuptake inhibitors Category Stimulants Category Local anesthetics Category Methyl esters nervous system drug stub ... more details
Orphan date December 2009 Unsourced image removed Image TBP Structure.PNG frame Apical and equatorial positions in trigonal bipyramidal structure Apicophilicity is the phenomenon in which Electronegativity electronegative substituents of orbital hybridisation trigonal bipyramidal pentacoordinate Chemical compound compounds prefer to occupy apical positions L sub ap sub ref http goldbook.iupac.org AT06990.html IUPAC Gold Book ref . The term apicophilicity was first proposed by Earl L. Muetterties in 1963 for the structural analysis of pentacoordinate phosphorus fluoride s by sup 19 sup F Nuclear magnetic resonance NMR . Since the apical bonding of a pentacoordinate typical Periodic table group 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 substituent s, 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 isomer ic structures in which the substituent occupies an apical position and an equatorial position L sub eq sub . Experimentally, instead of direct measurement of the energy difference, which is usually difficult to measure, the relative energy barrier s for pseudorotation of isomers are used for determination of the apicophilicity scale. Some experimental and theoretical studies have been made to measure relative apicophilicities for various substituents. The apicophilicity of a substituent mainly depends on its electronegativity, but some other factors can also have an effect. A bulky substituent prefers equatorial positions, which are more distant from other substituents. A substituent with pi bond bonding ability also prefers equatorial 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 c ... more details
The C&minus H bond Use &minus , not &ndash , for a schematic single bond is a covalent bond bond between carbon and hydrogen atoms, most commonly found in organic compound s. ref name March JerryMarch ref Carbon hydrogen bonds have a bond length of about 1.09 ngstr m 1.09 10 sup &minus 10 sup m and a bond energy of about 413 Joule kJ Mole unit mol see table below . Using electronegativity Pauling s scale C 2.5 and H 2.1 the electronegativity difference between these two atoms is 0.4. Because of this small difference in electronegativities, the C&minus H bond is generally regarded as being non polar. In structural formula s of molecules, the hydrogen atoms are often omitted. Compound classes consisting solely of C&minus H bonds and carbon carbon bond C&minus C bonds are alkane s, alkene s, alkyne s, and aromatic hydrocarbon s. Reactions The C&minus H bond in general is unreactive. In several compound classes, collectively called carbon acid s, the C&minus H bond can be sufficiently acidic for proton removal. Unactivated C&minus H bonds are found in alkanes and are not adjacent to a heteroatom O, N, Si, etc. . Such bonds usually only participate in radical substitution . Another reaction type involving C&minus H bonds is so called C H bond activation mediated by metals and carbene C H insertion . Although the C&minus H bond is one of the strongest, it varies over 30 in magnitude for fairly stable organic compounds, even in the absence of heteroatoms. ref http www.cem.msu.edu reusch OrgPage bndenrgy.htm dissbe ref class wikitable style text align center Bond Hydrocarbon radical Bond Dissociation Energy kcal mole CH sub 3 sub &minus H Methyl 103 C sub 2 sub H sub 5 sub &minus H Ethyl group Ethyl 98 CH sub 3 sub sub 2 sub HC&minus H Isopropyl 95 CH sub 3 sub sub 3 sub C&minus H tert Butyl 93 CH sub 2 sub CH&minus H vinyl 112 C sub 6 sub H sub 5 sub &minus H phenyl 110 CH sub 2 sub CHCH sub 2 sub &minus H Allyl 88 C sub 6 sub H sub 5 sub CH sub 2 sub &minus H Benzyl 85 ... more details
Refimprove date February 2007 A diagonal relationship is said to exist between certain pairs of diagonally adjacent chemical element element s in the second and third periods of the periodic table . These pairs lithium Li and magnesium Mg , beryllium Be and aluminium Al , boron B and silicon Si etc . exhibit similar properties for example, boron and silicon are both semiconductor s, forming halides that are hydrolysed in water and have acidic oxides. Such relationship occurs because crossing and descending the periodic table have opposite effects. On moving across a period of the periodic table, the size of the atom s decreases, and on moving down a group the size of the atoms increases. Similarly, on moving across the period, the elements become progressively more covalent , less basic and more Electronegativity electronegative , whereas on moving down the group the elements become more ion ic, more basic and less electronegative. Thus, on both descending a group and crossing the period by one element, the changes cancel each other out, and elements with similar properties which have similar chemistry are often found the atomic size, electronegativity, properties of compounds and so forth of the diagonal members are similar. It is found that the chemistry of a first row second period element often has similarities to the chemistry of the second row third period element being one column to the right of it in the Periodic Table. Thus, the chemistry of Li has similarities to that of Mg, the chemistry of Be has similarities to that of Al, and the chemistry of B has similarities to that of Si. These are called diagonal relationships NB It is not as noticeable after B and Si . The reasons for why diagonal relationships exist are not fully understood, but charge density is a factor. For example, Li is a small cation with a 1 charge and Mg2 is somewhat larger with a 2 charge, so the charge density on each ion is roughly the same. Using the Li Mg pair under room temperature ... more details
orphan date August 2010 Infobox software name EleMints logo File EleMints icon.png 128px screenshot File EleMints screenshot.png 220px A screenshot of EleMints caption EleMints screenshot author Dimitri Bouniol developer App Kainime, Mochi Development, Inc. latest release version 2.0 latest release date start date and age 2011 11 10 operating system iOS platform iPhone , iPod Touch , iPad language English genre Periodic table license commercial software Commercial website URL www.elemintsapp.com EleMints is a periodic table application software application distributed on the App Store iOS App Store . It was developed by Dimitri Bouniol. It features a periodic table , plot graph, element listing, article database, and molar mass calculator. Periodic table The periodic table can be colored in a variety of ways depending on what property is chosen. Supported properties are classification, electronegativity , melting point , boiling point , state of matter physical state , density , specific heat , crystal structure , empirical atomic radius , calculated atomic radius, covalent radius , Van der Waals radius , triple bond covalent radius , metallic radius , atomic weight , period periodic table period , group periodic table group , block, number of proton s, neutron s, nucleon s, and proton neutron ratio. ref cite web url http www.appkainime.com software elemints userguide.html title EleMints User Guide publisher App Kainime ref The periodic table can also be zoomed by performing a pinch gesture. On zooming, crystal structure and physical state diagrams are present. Plot graph The plot graph provides a way to analyze how certain properties change across a period periodic table period or down a group periodic table group . Supported properties are classification, electronegativity, melting point, boiling point, physical state, density, specific heat, oxidation state , empirical atomic radius, calculated atomic radius, covalent radius, Van der Waals radius, triple bond cov ... more details
electron density around the oxygen atoms due to their higher electronegativity compared to the carbon ... with the greater electronegativity . The oxidation state view of the CO SUB 2 SUB molecule is shown ... most chemists agree that the difference in electronegativity between carbon in oxygen is insufficient ... more details
, because the small boron atoms fill the existing spaces between the rhenium atoms. Furthermore, the electronegativity electronegativities of rhenium and boron are close enough 1.9 and 2.04 on the Electronegativity Pauling electronegativity Pauling scale that they form covalent bonds in which the electrons ... more details
Seealso Resonance chemistry File Mesomeric effect M V.1.png thumb right 600px M effect of a methoxy group in an ether File Mesomeric effect M V.1.png thumb right 420px M effect of a carbonyl group in acroleine The mesomeric effect or resonance effect in chemistry is a property of substituent s or functional group s in a chemical compound . The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structure s and is symbolized by the letter M . The mesomeric effect is negative M when the substituent is an electron withdrawing group and the effect is positive M when based on resonance and the substituent is an electron releasing group. Examples of M substituents acetyl IUPAC ethanoyl nitrile Nitro compound nitro Examples of M substituents alcohol amine benzene The net electron flow from or to the substituent is determined also by the inductive effect . The mesomeric effect as a result of p Atomic orbital orbital overlap resonance has absolutely no effect on this inductive effect, as the inductive effect is purely to do with the electronegativity of the atoms and their topology in the molecule which atoms are connected to which . The concepts of mesomeric effect, mesomerism and mesomer were introduced by Christopher Kelk Ingold Ingold in 1938 as an alternative to the Linus Pauling Pauling s synonymous concept of resonance effect resonance . ref If It s Resonance, What Is Resonating? Kerber, Robert C. . J. Chem. Educ. 2006 83 223. http www.jce.divched.org Journal Issues 2006 Feb abs223.html Abstract ref Mesomerism in this context is often encountered in German and French literature but in English literature the term resonance dominates. Mesomerism in conjugated systems Mesomeric effect can be transmitted along any number of carbon atoms in a conjugated system . This accounts for the resonance stabilization of the molecule due to delocalization of charge. See also List of publication ... more details
Unreferenced auto yes date December 2009 In physics , polarity is a description of an attribute, typically a binary attribute one with two values , or a Euclidean vector vector a direction . For example An electric charge has a polarity of either positive or negative. A battery contains polarity, with the two and terminals. Similar to electric charge, the energy flows from the positive terminal, through the battery, to the negative terminal, and exits the dry cell. A voltage has a polarity, in that it could be positive or negative with respect to some other voltage, such as the one at the other end of a battery electricity battery or electric circuit . A magnet has a polarity, in that one end is the north and the other is the south . The Spin physics spin of an entity in quantum mechanics has a polarity positive or negative. Polarized light has waves which all line up in the same direction. Chemical polarity is a feature of chemical bond s, where two different atom s in the same molecule have different electronegativity . As a result, the electrons in the bond are not shared equally by the two atoms. This causes an asymmetrical polar electric field. Molecular covalent bond s can be described as polar or nonpolar. Entire molecules can also be described as polar. See also In phase Phase cancellation Phase difference Wiktionary DEFAULTSORT Polarity Physics Physics stub Category Physics bs Polarnost de Polarit t Physik es Polaridad f sica eo Poluseco fr Polarit hr Polarnost io Polareso id Polaritas fisika nl Polarisatie scheikunde ja pl Polarno pt Polaridade simple Polarity sr sh Polarnost ... more details
Image Allyl silatrane from xtal 3D balls.png thumb right 170px Ball and stick model of the allyl silatrane molecule An Atrane is a tricyclic molecule with three five membered rings. It has a Transannular interaction transannular dative bond by a nitrogen atom , depicted as A. The name atrane was first proposed by Mikhail Grigorievich Voronkov ru , , . Image Atranes.svg thumb center 500px From left to right atrane, quasiatrane and proatrane Various atranes are named depending on the central Chemical element element , e.g. silatrane E silicon boratrane E boron phosphatrane E phosphorus , etc. It is also proposed that when Y nitrogen, the prefix aza be inserted before element atrane azasilatrane, for example because atranes wherein E silicon and Y oxygen have been referred to as just silatranes . ref John G. Verkade Main group atranes chemical and structural features Coordination Chemistry Reviews volume 137 1994 233 295 233. ref Silatranes exhibit unusual properties as well as biological activity in which the coordination of nitrogen to silane plays an important role. Some derivatives such as phenylsilatrane are highly toxic. The transannular coordinate bond in atranes can be stretched quasiatranes, B and even broken proatranes, C by controlling their stereoelectronic properties. Proazaphosphatrane is a very strong non ion ic Base chemistry base and is utilized in various types of Organic compound organic Chemical synthesis synthesis as an efficient catalyst . In 2000, Robert R. Holmes and his co workers reported a new class of silatranes that contain three six membered rings and revealed that these atranes have weaker nitrogen donor interaction in comparison with corresponding ones bearing three five membered rings. The degree of the interaction depends mainly on the electronegativity effects of an exocyclic ligand . References references commons category atranes Category Heterocyclic compounds Category Spiro comp ... more details
Encyclopedia
top
