Where results make sense

About us   |   Why use us?   |   Reviews   |   PR   |   Contact us

Molecular Mechanics In effect, "A" determines the degree of "stickiness" of the van der Waals attraction and "B" determines the degree of "hardness" of the atoms (e.g marshmallow-like, billiard ball-like, etc.). The electrostatic contribution is modeled using a Coulombic potential. The electrostatic energy is a function of the charge on the non-bonded atoms, their interatomic distance, and a molecular dielectric expression that accounts for the attenuation of electrostatic interaction by the environment (e.g. cmm.info.nih.gov /modeling/guide_documents/molecular_mechanics_document.html   (1070 words)

CHEM 102/105 Section H1 Glossary Electrostatic (coulombic) attraction between charges of opposite sign of adjacent molecules with permanent dipole moments. Attraction between fleeting dipoles induced in neighbouring atoms or molecules by momentary polarisations (distortions) of an electron cloud. A gas for which the volume of the particles is tiny compared to the volume of the gas (i.e., to the volume of the container), and there are no forces of attraction or repulsion between the particles. www.chem.ualberta.ca /~njones/midtermglossary.html   (795 words)

Coulomb Figure 1 illustrates a torsion balance like Coulomb used to determine the relationship of the distance between charged objects and the force of their interaction. As the balls suspended from the thin fiber rotate toward the one attached to a glass rod, Coulomb was able to measure the torsion on the fiber with the scale near the top of the device and the distance between the balls on the scale that circumscribed the jar. It is instructive to compare the form of the mathematical expressions of Newton's Law for the gravitational attraction between two planetary bodies and Coulomb's Law for the electrostatic attraction between two charged particles. www.usm.maine.edu /~newton/Chy251_253/Lectures/CoulombsLaw/Coulomb.html   (746 words)

Coulombic attraction Coulombic attraction: Encyclopedia II - Corrosion - Corrosion in passivated materials Coulombic attraction: Encyclopedia II - Corrosion - Electrochemical theory Coulombic attraction holds these oppositely-charged particles together, but there are other sorts of negative charge which are also attracted to the metal ions, such as the negative ions (anions) in an electrolyte. www.experiencefestival.com /coulombic_attraction   (606 words)

The Thomas Group - PTCL, Oxford In water the Coulombic attraction of the two oppositely charged ions drops by a factor of 80 (the dielectric constant of water) and the dissociation constant changes to 7, i.e. However, in a solution of this concentration the Coulombic interaction between a pair of ions is similar to that between neighbours in comparable uncharged liquids at a distance of more like 3 nm. A given central ion exerts a simple Coulombic force on ions in the first "shell of ions" but after this the Coulombic force is screened by this shell of ions and becomes progressively more screened as the distance increases. ptcl.chem.ox.ac.uk /~rkt/lectures/liqsolns/electrolyte_solutions.html   (1406 words)

Solubility of Ionic Compounds   (Site not responding. Last check: ) We have discussed dipole-dipole bonding in some detail and we recognize that this bonding arises because of the Coulombic attraction of two dipoles for one another. A dipolar molecule has a q that is less than one, but an ion has some integer charge (chloride is -1, sodium is +1, etc.) A dipole-ion attraction should actually be stronger than a dipole-dipole attraction, although it is less strong than the ionic attractions in the ionic solid. The extent to which an ionic compound is soluble in a solvent is dependent upon the polarity of the solvent. neon.chem.uidaho.edu /~honors/ionicsol.html   (393 words)

Ab Initio Calculation of Salicylic Acid Adsorbed on the Titanium Oxide Particle Recent Progress: We investigate the effect of coulombic interactions on the mobility of rhodamine 6G (R6G) and Oregon Green 514 (ORG) in sol-gel silicates by measuring their mobility distributions using single molecule polarization measurements. To examine the effect of coulombic interaction on guest-host interaction, we report the mobility measurement of rhodamine 6G (R6G) and Oregon Green 514 (ORG) encapsulated in silica sol-gel thin films. The effect of coulombic interaction was readily observed when more tumbling ORG than R6G molecules were found in sol-gel silicates. www.geneseo.edu /~yokoyama/singlemolecule   (897 words)

[No title]   (Site not responding. Last check: ) The wave functions ``of the beam" which minimize it are shown to satisfy the corresponding non-linear coupled set of Schroedinger-like equations in distributional sense. The second half of the text is devoted to a three-dimensional analogue of this result, somewhat more artificial in requiring an electrostatic confinement in the third dimension of course, and somewhat more interesting as admitting even a weak Coulombic attraction. 32 (1999) L87] where precisely the possibility of the existence of Coulombic attraction of equal (i.e., formally, purely imaginary) charges has been advocated as emerging within the so called PT symmetric quantum electrodynamics. gemma.ujf.cas.cz /~znojil/hartree.txt   (232 words)

Bonds-vs-Interactions Because ionic and covalent bonding uses electrostatic attractions between areas of full charge, the resulting force of attraction is strong. Definition: Intermolecular Forces are electrostatic forces of attraction that exist between an area of negative charge on one molecule and an area of positive charge on a second molecule. Because the molecules are polar, the force is either a dipole-dipole attraction or a Hydrogen bond. www.bcpl.net /~kdrews/interactions/interactions.html   (1237 words)

ScienceWeek This is due to Coulombic repulsions between charged groups along the polymer chain, forcing the polymer into an extended rodlike conformation. The structure-property relationships of polyampholytes are dictated by Coulombic attractions between anionic and cationic species on different monomer units. Long-range attractive van der Waals forces are ubiquitous and must be balanced by Coulombic, steric, or other repulsive interactions to engineer the desired degree of colloidal stability. scienceweek.com /2003/sw030919.htm   (5269 words)

Structural Chemistry   (Site not responding. Last check: ) Structural chemistry is the study of the relationship between chemical bonding and bond orientation, atom size and valence, and atomic packing arrangements and the internal structure of crystalline materials. Physical and chemical properties of mineral crystals are influenced to a major extent by the spatial distribution of constituent atoms within three-dimensional structures and by the interatomic forces of attraction and repulsion occurring between their constituent atoms. He further advanced the hypothesis that the energy of electrons was quantized; i.e., there are only a restricted number of stable orbits possible, associated with certain energy levels, and not, as previously thought, an infinite number of possible stable orbits. www.soils.agri.umn.edu /academics/classes/soil5311/Lectures/notes/structural_chemistry.html   (4358 words)

Alchemy :: Chemistry : Chemical Bonding   (Site not responding. Last check: ) The force of attraction which holds together atoms in molecules and crystals is called a chemical bond. Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. Unlike ionic bonds, where ions are held together by a non-directional coulombic attraction, covalent bonds are highly directional. alchemy-education.com /Chem/Bond.html   (736 words)

Electronic Hamiltonian - Wikipedia, the free encyclopedia The potential energy between the electrons and nuclei - the total electron-nucleus Coulombic attraction in the system; The potential energy arising from Coulombic electron-electron repulsions The potential energy arising from Coulombic nuclei-nuclei repulsions - also known as the nuclear repulsion energy. en.wikipedia.org /wiki/Electronic_Hamiltonian   (482 words)

feat10 In the Coulombic attraction theory (CAT), first proposed by Sogami in 1983, the mean field interaction between charged particles has a weak, long-range attraction via their counterions, whereas in DLVO theory the long-range interaction is purely repulsive. Attempts to apply DLVO theory to the phenomenon failed and the system was thought to be `anomalous', until the case was reopened by neutron scattering in the late 1980's when some experiments at the ILL in Grenoble gave strong indications that the vermiculite system was governed by the long-range Coulombic attraction predicted by Sogami. The installation of the new high-angle detector bank on LOQ has improved these studies immensely, because it is now possible to observe diffraction effects from the collapsed crystalline phase (region III) of the system, as shown in figure F10.3. www.isis.rl.ac.uk /isis98/feat10.htm   (1012 words)

Coulombic Attraction A comparison between the RKR potential energy curves of the states and the simple Coulombic attraction between S Note the close match between the outer wall of the ion pair potential and the Coulombic attraction of the two ions. The bond length at the minimum of the ion pair potential well can also be seen to be close to that of the sum of the radii of the S www.chm.bris.ac.uk /pt/laser/western/s2/coulomb.htm   (78 words)

Chemistry 1020--Spring 2000  Lecture 14 Notes The force of attraction depends on the size of the charge on the ion and the distance between them. When hydrogen atoms are attached to very electronegative, very small atoms (specifically F, O, and N), the polarity of the bond is very great, and the positive end of the bond at the hydrogen atom is capable of getting very close to and interacting with the lone pairs on other F, O, or N atoms. These bonds are considered special because the strength of attraction is quite a bit more than the attraction between dipoles. www.chem.fsu.edu /editors/rlight/1020s00/lecture14.htm   (1334 words)

Shriver & Atkins, Inorganic Chemistry, 3rd edition   (Site not responding. Last check: ) The Coulombic attraction of nearest-neighbor cations and anions accounts for the bulk of the lattice enthalpy of an ionic compound. The nearest neighbor Coulombic attraction depends upon the ion charges and the distance between the ions. The changes in distance between ions is relatively small compared to the unit changes found in the ion charges, so MgO (+2, —2) has a roughly 4× larger lattice enthalpy than NaCl or LiF (+1, —1). bilbo.chm.uri.edu /CHM401/Exercise2_17.htm   (158 words)

Response to """Comments on 'Diffuse double-layer models, long-range forces, and ordering of clay colloids'""" -- ... to the magnitude of the electrostatic attraction force, as it Coulombic attraction theory exposes significant errors in the That is, the Coulombic contribution to colloid pressure soil.scijournals.org /cgi/content/full/67/6/1961   (1764 words)

Ionic Bonding   (Site not responding. Last check: ) to be stronger than covalent bonds due to the coulombic attraction between. The atoms are joined by chemical bonds which are forces of attraction that hold atoms together. Ionic bonds and Compounds: bonding is the result of the attraction of oppositely charged ions (atoms. ionicbonding.flobonds.info   (733 words)

The Bohr atom In 1913 the Danish physicist Niels Bohr proposed that the structure of the hydrogen atom can be approached by assuming that the electron is held in its orbit by equating the force required to accelerate it into a circular orbit with the coulombic attraction between nucleus and electron. The term on the RHS is the coulombic attractive force. The total energy of the electron is given by the sum of the kinetic and potential energies. www.tannerm.com /Quick_atom/A4.htm   (618 words)

Bright prospects for laboratory lasers Science News - Find Articles At this intensity, the electric field of alaser pulse that is shined on an atom is strong enough to compete for electrons with the nucleus's electric attraction, called the coulombic field. Ryszard Gajewski, director of the Division of Advanced Energy Projects at the U.S. Department of Energy in Germantown, Md., predicts that within half a year, the three groups will be producing pulses with electric fields that are much greater than the coulombic field. "If an electron's behavior is controlled by the laser field rather than the coulombic attraction of the nucleus, that's altogether a new regime. www.findarticles.com /p/articles/mi_m1200/is_v131/ai_4722673   (351 words)

SparkNotes: Ionic Bonds: Ionic Bonding As we shall explore in this section on ionic bonding, ionic bonds result from the mutual attraction between oppositely charged ions. They tend to be stronger than covalent bonds due to the coulombic attraction between ions of opposite charges. To maximize the attraction between those ions, ionic compounds form crystal lattices of alternating cations and anions. www.sparknotes.com /chemistry/bonding/ionic/summary.html   (207 words)

Chapter 4 - Solutions A crystal of sodium chloride contains Na and Cl ions held together by the Coulombic attraction between cations (Na and anions (Cl Water is a molecular substance, meaning the hydrogen and oxygen share electrons. When an ionic solid such as NaCl dissolves in water, the positive ends of the water molecule (hydrogen ends) are attracted to the negatively charged anions and the negative ends of the water molecule (oxygen end) are attracted to the positively charged cations. The interaction between polar solvent molecules and ions allows a large part of the Coulombic attraction present in an ionic crystal to be maintained in solution. www.chemistry.ohio-state.edu /~woodward/ch121/ch4_solns.htm   (924 words)

14        Loose compounds and solutions Given the strong Coulombic attraction between Na and Cl ions in solid sodium chloride, it is at first sight surprising that the latter should dissolve in water. pointing towards them, considerable Coulombic attraction is generated, enough presumably to dissolve the ions. For some cations, this attraction may be supplemented by some degree of dative bonding. www.hull.ac.uk /chemistry/intro_inorganic/Chap14.htm   (607 words)

Types of Atomic Bonding   (Site not responding. Last check: ) The transfer of electrons results in a positively charged ion and a negatively charged ion, which are drawn to each other by coulombic attraction until their filled electron shells overlap. A high difference between the electronegativity of two atoms increases their tendency to form an ionic bond. The assymetric charge distribution in dipoles can draw them to each other by coulombic attraction, bonding them together. www.semiconphysics.com /bonding-types.htm   (456 words)

Sodium, Hydrogen Halides and Melting Although dispersion forces are important here as well, they are much weaker than the Coulombic interaction between the ions and so we need to only focus on the Coulomb interactions to understand the trend. This law says that the attraction get weaker as the halide ion gets bigger, because the center of positive charge on the Na+ is farther away from the center of negative charge on the halide. Since the ionic radius increases as you go down the column, the Coulomb attraction gets weaker as you go from NaCl to NaBr and the melting point becomes lower as a result - although the dispersion force increases, it does not increase by nearly as much as the coulomb attraction decreases. www.newton.dep.anl.gov /askasci/chem03/chem03693.htm   (309 words)

Collisions of Propanol, Carbon Dioxide and Water with Molten NaOH/KOH The polymer molecule is modeled as a charged bead spring chain, counter ions to the polymer and the wall are modeled as charged spheres and the solvent as an uncharged sphere. The chain, which has a globular conformation in poor solvents, adsorbs in a flat pancake conformation at high charge densities due to Coulombic attraction to the oppositely charged surface. The size of the chain on the surface shows a nonmonotonic dependence on the surface charge density of the wall but decreases monotonically with solvent quality. www.chem.wisc.edu /physical/Abstracts/Fall04/reddy.htm   (189 words)

Diffuse Double-Layer Models, Long-Range Forces, and Ordering in Clay Colloids -- McBride and Baveye 66 (4): 1207 -- ... attraction as would an increase in particle density. attraction is attributed to the rearrangement and confinement Depiction of particle-particle Coulombic interaction according to Sogami–Ise model at low and high particle charge, leading to repulsive (a) and attractive (b) interaction. soil.scijournals.org /cgi/content/full/66/4/1207   (6269 words)

Chapter6.htm ; (2) the coulombic potential energy of the electrons attracted to the nucleus (-Ze /r); and (c) the electron-electron (e-e) repulsion term. To get an estimate of how large this term is, let us use the (perhaps inadequate) guess for our wavefunction to evaluate it. The exchange integral K has no classical counterpart and may be considered as a correction term to the coulombic interaction arising when the two electrons have the possibility of "exchanging" orbitals. www.rci.rutgers.edu /~kroghjes/KK-J421521/Chapter7.htm   (1598 words)

Try your search on: Qwika (all wikis)

About us   |   Why use us?   |   Reviews   |   Press   |   Contact us   Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.