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Topic: Van der Waals radius

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Johannes Diderik van der Waals

Van der Waals Bonding

Van der Waals

Van der Waals equation

Johannes van der Waals

Van der Waals force

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	Johannes Diderik van der Waals - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-22)
		Johannes Diderik van der Waals (November 23, 1837 – March 8, 1923) was a Dutch scientist famous "for his work on the equation of state for gases and liquids", for which he won the Nobel Prize in physics in 1910.
		Van der Waals was the first to realise the necessity of taking into account the volumes of molecules and the intermolecular forces (now generally called "van der Waals forces") in establishing the relationship between the pressure, volume and temperature of gases and liquids.
		Van der Waals was born in Leiden, the Netherlands, as the son of Jacobus van der Waals and Elisabeth van den Burg.
	www.sevenhills.us /project/wikipedia/index.php/Johannes_Diderik_van_der_Waals (297 words)

	Van der Waals radius (Site not responding. Last check: 2007-10-22)
		Van der Waals radii are determined from measurements of atomic spacing between pairs of unbonded atoms in crystals.
		The van der Waals radius is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics.
		The other term that is introduced in the van der Waals equation, a/V 2, describes a weak attractive force among molecules, which increases as V decreases and molecules become more crowded together.
	www.sciencedaily.com /encyclopedia/van_der_waals_radius (383 words)

	Encyclopedia: Van der Waals equation (Site not responding. Last check: 2007-10-22)
		The van der Waals equation is an equation of state for a fluid composed of particles that have a non-zero size and a pairwise attractive inter-particle force (such as the van der Waals force.) It was derived by Johannes Diderik van der Waals in 1873, based on a modification of the ideal gas law.
		In chemistry, the term Van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules.
		The atomic radius is the distance from the atomic nucleus to the outmost stable electron orbital in a atom that is at equilibrium.
	www.nationmaster.com /encyclopedia/Van-der-Waals-equation (1225 words)

	Van der Waals radius -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		The van der Waals radius of an ((physics and chemistry) the smallest component of an element having the chemical properties of the element) atom is the radius of an imaginary hard (A particular environment or walk of life) sphere which can be used to model the atom for many purposes.
		Van der Waals radii are determined from measurements of atomic spacing between pairs of unbonded atoms in (A crystalline element used as a component in various electronic devices) crystals.
		The van der Waals radius is named after (Dutch physicist (1837-1923)) Johannes Diderik van der Waals, winner of the 1910 (Click link for more info and facts about Nobel Prize in Physics) Nobel Prize in Physics.
	www.absoluteastronomy.com /encyclopedia/V/Va/Van_der_Waals_radius.htm (437 words)

	CONK! Encyclopedia: Van_der_Waals_radius (Site not responding. Last check: 2007-10-22)
		The van der Waals radius of an atom is the radius of an imaginary hard sphere which can be used to model the atom for many purposes.
		Particularly useful and well known is the van der Waals equation of state:
		In the equation of state, this volume of exclusion (a) should be subtracted from the volume of the container (V), thus: (V - b).
	www.conk.com /search/encyclopedia.cgi?q=Van_der_Waals_radius (304 words)

	Periodicity of Atomic Properties
		The radius of anions is always larger than the covalent radius of the atoms from which they are derived, as shown in the figure on the right, which applies to the Group VII elements.
		Note that the difference between the van der Waals radius of an atom and the ionic radius of its anion is not significant.
		The van der Waals radius is the radius of the spherical space occupied by an atom when it is bonded to another atom by van der Waals forces.
	www.physchem.co.za /Atomic/Periodicity.htm (1122 words)

	Deviations from Ideal Gas Law Behavior: (Site not responding. Last check: 2007-10-22)
		Van der Waals realized that two of the assumptions of the kinetic molecular theory were questionable.
		Van der Waals proposed that we correct for the fact that the volume of a real gas is too large at high pressures by subtracting a term from the volume of the real gas before we substitute it into the ideal gas equation.
		According to the table of van der Waals constants, the volume of a mole of argon atoms is 0.03219 liters.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch4/deviation5.html (1258 words)

	IMB Jena Image Library - Structural Biology Glossary: Van der Waals radii
		Van der Waals radii are determined from contact distances between non-bonded atoms.
		In spacefilling representations of biopolymers shaded spheres of atoms are shown and often van der Waals radii are adopted for calculating the atom spheres.
		The van der Waals radius defines the volume and surface of an atom or molecule.
	www.imb-jena.de /ImgLibDoc/glossary/IMAGE_VDWR.html (467 words)

	Atomic Size HTML
		The covalent radius for the chlorine atom is 0.099 nm.
		The Van der Waals radius refers to the situation when the atoms are adjacent but not bonded.
		The Van der Waals radius for chlorine is 0.180 nm.
	www.alevelchemistry.co.uk /Module_1/HTML_Pages/Atomic_Size_HTML.htm (685 words)

	The Chem-Ray Homepage (Site not responding. Last check: 2007-10-22)
		When drawings are made in the ball and stick format, this van der Waals radius for each element is multiplied by the atom radius factor.
		Bond Radius (.01 Angstroms): The bond radius command is used to specify the radius of the bonds in Angstroms in the actual pictures.
		H-Bond Radius (.01 Angstroms): The H-bond radius command is used to specify the radius of the hydrogen bonds in Angstroms in the actual pictures.
	www.chem.sunysb.edu /msl/chemray/options.html (653 words)

	atomic and ionic radius
		The radius of an atom can only be found by measuring the distance between the nuclei of two touching atoms, and then halving that distance.
		This measure of atomic radius is called the van der Waals radius after the weak attractions present in this situation.
		If you think about it, the metallic or covalent radius is going to be a measure of the distance from the nucleus to the electrons which make up the bond.
	www.chemguide.co.uk /atoms/properties/atradius.html (925 words)

	van der Waals Equation of State
		It is usually referred to as the van der Waals equation of state.
		Since the constant b is an indication of molecular volume, it could be used to estimate the radius of an atom or molecule, modeled as a sphere.
		In the periodic table is found an atomic radius of 0.075 nm for nitrogen, so the above estimate for a nitrogen molecule is plausible.
	hyperphysics.phy-astr.gsu.edu /hbase/kinetic/waal.html (408 words)

	Molecular surface and volume * To whom it may concern: Fig 6.17 (img100.gif) not found *
		In geometric terms, the van der Waals radius can be imagined as a spherical ``shield'' surrounding the atom, and the closest distance between two non-bonded atoms is when their respective shields touch.
		For all practical purposes, the van der Waals surface of these oddments cannot enter into contact with a solvent or a drug molecule and therefore is not truly an accessible surface.
		As a result, the area where the probe touches the van der Waals surface is called the contact surface, the center of the spherical probe traces a surface called the solvent accessible surface and the patches over narrow gaps and clefts traced by the surface of the probe are called re-entrant surfaces.
	www.ccl.net /cca/documents/molecular-modeling/node5.html (1759 words)

	Hydrogen bond radii for the hydrogen halides and van der Waals radius of hydrogenePrints@IISc - Open Access Archive of ... (Site not responding. Last check: 2007-10-22)
		It is noted that the radius of H atom in HF, HCl, HBr, and HCN are, respectively, 0.55±0.07, 0.74±0.08, 0.80±0.11, and 0.93±0.07 Å.
		From this correlation the radius of H atom in HI is estimated to be 0.90±0.11 Å.
		By extrapolating to zero dipole moment, the van der Waals radius of H atom is determined to be 1.0±0.1 Å, reasonably close to the value proposed by Pauling, 1.2 Å.
	eprints.iisc.ernet.in /archive/00002486 (234 words)

	2.5.1 The van der Waals Equation
		So van der Waals argued that in the ideal gas law V should be replace by V - nb, the actual volume available to the gas.
		Van der Waals accounted for those by reasoning as follows: pressure is caused by impacts of molecules on the walls of the container holding a gas.
		The result of these two changes is van der Waals' equation 2.5.1.
	scholar.chem.nyu.edu /0651/notes/pchem/node25.html (647 words)

	ROCO Chapter 1 : Space-filling Models
		Van der Waals radii are used to construct a special kind of molecular model called a space-filling model.
		These models are constructed by drawing each atom as a van der Waals sphere with the atom’s nucleus at the center of the sphere.
		Distance measurements confirm that the nonbonded OH distance (1.8 Å) is much shorter than the sum of the van der Waals radii (1.2 + 1.4 = 2.6 Å).
	academic.reed.edu /chemistry/roco/Geometry/space_filling.html (316 words)

	Volume 1 Chapter 7 Using van der Waals Radii for Distance Testing (Site not responding. Last check: 2007-10-22)
		If the van der Waals radii and/or tolerance are to be changed from the standard values then the VDW-RAD command must be used before the CONTACT command is defined.
		van der Waals distance searching is particularly useful when a contact can have more than one element type as would happen when an ELDEF instruction is used.
		If van der Waals distance searching is used, the test distance will depend on whether TZ has been matched to an oxygen or sulfur.
	www.gh.wits.ac.za /csds/volume1/z1c07076.html (578 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		A sphere of 1 A radius is generated at the (0, 0, 0) coordinates using the dot density specified by the user.
		For each atom (Ai), this sphere is scaled multiplying the dot coordinates by the correspondent Van Der Waals radius (Ri) and translated to the atom coordinates (Xi, Yi, Zi).
		This procedure is performed measuring the distance between the surface dots of the "Ai" atom and all atomic coordinates for all "n" atoms: if it's less than the "An" Van der Waals radius, the dot is overlapped.
	arcib.dowling.edu /~CSC181F02/vega.txt (96 words)

	Intermolecular force - Wikipedia, the free encyclopedia
		These are fundamentally electrostatic interactions (ionic interactions, hydrogen bond, dipole-dipole interactions) or electrodynamic interactions (van der Waals/London forces).
		Electrostatic interactions are classically described by Coulomb's law; the basic difference between them is the strength of their charge.
		Also called London forces, instantaneous dipole effects or Van der Waals forces, these involve the attraction between temporarily induced dipoles in nonpolar molecules.
	en.wikipedia.org /wiki/Intermolecular_force (458 words)

	Van der Waals Interaction
		In fact, the macroscopic contribution to the van der Waals force is the same in each of the three systems described below, as it depends only on the tip-surface separation, macroscopic sphere radius, cone-angle and Hamaker constant of the system.
		All these quantities are identical in each system we look at, so that the van der Waals force acts as a background attractive force independent of the microscopic properties of the system.
		This effectively means that only the top layer of the sample contributes to the van der Waals force, and there are not enough ions in that layer for it to be significant.
	www.fyslab.hut.fi /~asf/physics/thesis1/node80.html (314 words)

	Van der Waals equation -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		We now stop treating the fluid's constituent particles as point particles, instead modelling them as hard spheres with a small radius (the (Click link for more info and facts about van der Waals radius) van der Waals radius.) Denoting the volume of each sphere by b, we modify the equation of state to
		This is also known as the (Click link for more info and facts about Principle of corresponding states) Principle of corresponding states.
		In the sense that we have eliminated the appearance of the individual material constants a and b in the equation, this can be considered unity in diversity.
	www.absoluteastronomy.com /encyclopedia/V/Va/Van_der_Waals_equation.htm (520 words)

	General Chemistry Online: FAQ: Liquids: What are van der Waals forces?
		Van der Waals forces are much weaker than chemical bonds, and random thermal motion around room temperature can usually overcome or disrupt them.
		Van der Waals' forces include all intermolecular forces that act between electrically neutral molecules.
		Hydrogen atoms are very small (with an atomic radius of about 37 pm, they're smaller than any other atom but helium).
	antoine.frostburg.edu /chem/senese/101/liquids/faq/h-bonding-vs-london-forces.shtml (836 words)

	Encyclopedia: Van der Waals radius (Site not responding. Last check: 2007-10-22)
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		Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions.
		van der Waals Johannes Diderik van der Waals (November 23, 1837 – March 8, 1923) was a Dutch scientist famous for his work on the equation of state for gases and liquids, for which he won the Nobel Prize in physics in 1910.
	www.nationmaster.com /encyclopedia/van-der-Waals-radius (627 words)

	Botany online: Physical Chemistry - Chemical Bonds - Covalent Bonds - Weak Interactions
		Consequently, Van der Waals attractions are under physiological conditions only of importance, if as many atoms of a molecule as possible are engaged.
		Van der Waals attractions are additive and have thus a much greater impact on macro- than on small molecules.
		The coupling of a substrate to an enzyme is to a large extent stabilized by Van der Waals attractions.
	www.biologie.uni-hamburg.de /b-online/e18/18c.htm (1037 words)

	Van der Waals bonding
		Van der Waals bonding is a process by which water molecules are attracted[?] to each other, via electrostatic[?] forces.
		These forces hold water together, when it is in a liquid phase.
		The text of this article is licensed under the GFDL.
	www.ebroadcast.com.au /lookup/encyclopedia/va/Van_der_Waals_bonding.html (51 words)

	Appendix C
		The distance between two atoms or atom groups at which E = 0 defines the van der Waals radii for those two groups.
		Rm (the distance that corresponds to the minimum energy of interaction) is often somewhat longer that the van der Waals (vdW) radius (see Figure C.1).
		Table C.1 includes data for van der Waals radii and one-half Rm (the value of 1/2 Rm provides a radius comparable to the van der Waals radius), reflecting minimum and optimal distances of separation, respectively.
	www.cgl.ucsf.edu /home/glasfeld/tutorial/App/AppC.html (465 words)

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