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	UNIT 4 - PERIODIC TABLE (Site not responding. Last check: 2007-10-10)
		The atomic radius is a periodic property of the elements.
		The relation between atomic radius and atomic number can be interpreted in terms of the arrangement of electrons in the orbitals of atoms and in terms of nuclear charge.
		The normal covalent radius is the effective distance from the center of the nucleus to the outer valence shell of that atom in a typical covalent or coordinate bond.
	dwb.unl.edu /Chemistry/LearningObjectives/NY04.html (2326 words)

	Ionic Coordination and Pauling's Rules
		Ionic radius also increases with increasing coordination number, the electron cloud is drawn out by the presence of more surrounding ions.
		The relative sizes are indicated by the radius ratio of the coordinating atoms or ions.
		An ionic structure will be stable to the extent that the sum of the strengths of the electrostatic bonds that reach an ion equal the charge on that ion.
	www.tulane.edu /~sanelson/eens211/paulingsrules.htm (2124 words)

	notes2
		Ionic bonds form when an electron or electrons from atoms of one or more element are lost to atoms of another element or elements.
		The ionic radius of an ion of a particular element with a specified charge is a measure of the size of that particular ion.
		Ionic radius generally increases from (1) cation to anion, (2) low Z to high Z within a group, (3) high positive charge to low positive charge, (4) low negative charge to high negative charge, and (5) high Z to low Z over specific portions some periods (rare earths, actinides), (Fig.
	www.geo.umn.edu /courses/2303/notes/Notes2/notes02.html (818 words)

	Atomic Size and Interatomic Distance
		Ionic radii also depend on the configuration of the ion relative to its nearest neighbors, chiefly in terms of the number of surrounding ions.
		The ionic radius of oxygen is 1.3 Angstroms, and hence it is very large compared to the cations with which it commonly bonds.
		This radius ratio is consistent with 6-fold coordination (cf., Fig 4.24 in Klein and Hurlbut).
	darkwing.uoregon.edu /~jrice/geol_311/Structure.html (3062 words)

	Module 6
		Because the ionic radius of an ion is a measure of how far it is located from its nearest neighbour, the radius will vary depending on how those neighbours are arranged around it.
		Note that unlike the case for ionic bonding, in all three of these cases the bonding forces are confined to the individual group of atoms, i.e., the C, N and O atoms don't indiscriminately attract hydrogen atoms from all directions.
		For example, Cu (ionic radius 0.73 angstroms, electronegativity 2.0) does not easily substitute for Mg (ionic radius 0.72 angstroms, electronegativity 0.72) as its higher electronegativity means that Cu is associated with a much higher level of covalent bonding than Mg.
	www.soes.soton.ac.uk /staff/pmrp/GY102/module6/m6.html (3081 words)

	Untitled
		The ionic radius of an element is its share of the distance between adjacent ions in an ionic solid.
		For example, the distance between the magnesium cation and the oxide anion in magnesium oxide is 211 pm, the radius of the Mg ion is calculated from 205pm - 146 pm = 65 pm.
		Ionic radii are for ions isoelectronic with a noble gas as described above with, for example silicon as Si and hydrogen as H
	chem.salve.edu /chemistry/trends6.asp (464 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)

	atomic and ionic radius
		Unlike a ball, an atom doesn't have a fixed 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.
		Trends in atomic radius in Periods 2 and 3
	www.chemguide.co.uk /atoms/properties/atradius.html (925 words)

	Chem 101(SEAS) Ionic Crystal Structures
		For ionic compounds the bonding forces are electrostatic and therefore omni-directional.
		In these cases it is possible to visualize the structures in terms of a close packed arrangement of the larger anions, with the cations occupying the vacant interstices between the close packed layers.
		Radius Na = 1.02Å, radius Cl = 1.81Å; radius ratio = 0.563.
	www.seas.upenn.edu /~chem101/sschem/ionicsolids.html (1284 words)

	Index (Site not responding. Last check: 2007-10-10)
		The metallic radius is half the distance between the centres of neighbouring atoms in a metal.
		The covalent radius is the smaller of the two and this is expected as, in the molecule, the atoms are pulled together by their attraction for the electrons shared in the bond between them.
		For example, the distance between the magnesium cation and the oxide anion in magnesium oxide is 0.211 nm, the radius of the Mg ion is calculated from 0.205 nm - 0.146 nm = 0.065 nm.
	www.chemit.co.uk /java/rsc_periodicity (690 words)

	Earth Materials Module 3 (Site not responding. Last check: 2007-10-10)
		Because the ionic radius of an ion is effectively a measure of how far it is located from its nearest neighbour, the radius will vary depending on how those neighbours are arranged around it.
		If the radius ratio is greater than 0.414 the cation will still have octahedral coordination (N=6), but now the anions will be pushed apart slightly, so that they are no longer in direct contact.
		The octahedral coordination remains stable up to a radius ratio of 0.732, at which point the anions are pushed too far apart and the coordination number has to increase to 8.
	www.huxley.ic.ac.uk /Local/EarthSciUG/ESFirstYr/EarthMaterials/mrpalmer/EarthMaterials/Em/module3/m3.html (3133 words)

	Mycorrhizal Citations
		Tyler, G. Ionic charge, radius, and potential control root/soil concentration ratios of fifty cationic elements in the organic horizon of a beech (Fagus sylvatica) forest podzol.
		The R/S ratios were most clearly related to the ionic potential of the cationic elements studied, which accounted for approximately 60% of the variability in R/S among elements.
		The ionic charge of an element was more important than the ionic radius.
	mycorrhiza.ag.utk.edu /latest/latest04/04_9tyler1.htm (203 words)

	Ionic and Laserscan (Site not responding. Last check: 2007-10-10)
		Ionic are adapting their WFS to support GML3.0 with topology, while keeping its transactional behaviour.
		Radius Topology will allow simple feature data to be structured automatically as it is imported into Oracle.
		Ionic’s “OGC Enabler Suite” is an advanced Suite of Java components acting as interoperable middleware and designed to support deployment of Spatial Data Infrastructures implementing OGC interfaces.
	www.ionic.be /pressroom/laserscan.jsp (459 words)

	Feldspar Structure
		Since Na is in the middle of the ionic radius spectrum we might expect it to be compatible with all the other ions.
		It turns out, from actual mineralogy, that ionic radius is most important and charge balance and ordering are secondary.
		However, at low temperatures the difference in ionic radius begins to tell and the feldspar separates into discrete streaks and patches of K and Na feldspar.
	www.uwgb.edu /dutchs/PETROLGY/FeldsparStruct.HTM (1033 words)

	A2 unit trends and patterns lattice energy page
		That is, the formation of a solid ionic compound from its gaseous constituent ions.
		Another variable that can be changed with ionic compounds is the ionic radius.
		In general, the larger the ionic radius the lower the lattice enthalpy as the amount of interaction between the ions is smaller and the packing of the ions is less efficient :
	www.rjclarkson.demon.co.uk /tandp/latticeenthalpy.htm (450 words)

	Ionization Energy (Site not responding. Last check: 2007-10-10)
		You could characterize the radius of the atom as a limiting radius where a certain percentage of the electron charge will be found.
		If the crystalline composition is such that the ions can be considered to be in contact with each other, and you can determine the lattice spacing from x-ray diffraction, then you can imply the ionic radius.
		As might be expected, the ionic radius of negative ions is slightly larger than the covalent radius since they have extra electronic charge, and that of positive ions is slightly smaller.
	hyperphysics.phy-astr.gsu.edu /hbase/Chemical/atomrad.html (184 words)

	[No title]
		The ionic radius of an element is measured in angstroms (Ä).
		(ionic radius = 1.12) in eight-fold coordination with F
		Six-fold (octahedral) coordination is favored when the radius ratio is between 0.414 and 0.732
	www.gpc.edu /~dthieme/Homework/1121-Homework1.htm (303 words)

	All A: atomic radius Z: atomic radius (Site not responding. Last check: 2007-10-10)
		The atomic radius is the distance from the atomic nucleus to the outmost stable...
		Technically, the atomic radius is one half of the equilibrium internuclear distance...
		Atomic radius is taken as the covalent radius for non-metallic elements and as the metallic radius for metals.
	www.davidchuk.com /atomic_radius.html (324 words)

	Ionization Energy (Site not responding. Last check: 2007-10-10)
		In specifying values for the radius of an atom, one must keep in mind the fact that atoms are not hard spheres, and the electron distribution in the outer part of the atom does not have a sharp cutoff radius.
		The illustration above is a plot of "covalent radii" (from Ebbing) which are determined by measuring the bond lengths in the molecules of chemical compounds.
		The atomic radius is one of the parameters used in quantifying chemical bonds.
	hyperphysics.phy-astr.gsu.edu /hbase/chemical/atomrad.html (184 words)

	Ionic and Laserscan (Site not responding. Last check: 2007-10-10)
		Radius Topology is an advanced spatial processing environment that extends the standard Oracle9i database and provides dramatic improvements to the speed and quality of spatial data manipulation.
		Based in Liege, Belgium, Ionic Software is a provider of interoperable, enterprise-class products for the publishing, discovery, access, integration, and application of spatial data in support of core enterprise business functions.
		The IONIC Team has a worldwide reputation as the very best in the industry, with unique expertise in distributed systems and Java components for web mapping.
	www.ionicsoft.com /pressroom/laserscan.jsp (459 words)

	Media Portfolio
		The covalent radius is half the distance between the nuclei of the two I atoms in the I2 molecule.
		The atomic radius is the distance between the nucleus and the outside of the atom.
		Metallic radii are shown for Na and Mg, and ionic radii for Na+ and Mg2+.
	cwx.prenhall.com /bookbind/pubbooks/hillchem3/medialib/media_portfolio/08.html (768 words)

	IB Chemistry Periodicity - Wikibooks, collection of open-content textbooks
		Ionic radius increases due to increased electron shielding.
		Na->Ar (across period 3) : Atomic radius decreases due to increased nuclear charge -> greater attraction for electrons.
		Ionic radius decreases Na->Al (due to increased nuclear charge) jumps Al->Si (due to reversal of ionisation direction...increased electron-electron repulsion) decreases Si->Ar (due to increased nuclear charge).
	en.wikibooks.org /wiki/IB_Chemistry_Periodicity (296 words)

	Ionic and Covalent Binding - Introduction
		The total distribution of charge in LiF is, therefore, consistent with the ionic model Li corresponding to the transfer of the single 2s valence electron of lithium to the fluorine.
		The radii of the nonbonded charge distributions (the distance measured along the bond axis from a nucleus to the outermost contour of its nonbonded density) are also consistent with the ionic model.
		for the radius of the nonbonded charge density on fluorine is consistent with that of a fluoride ion distribution as it represents a slight increase over the atomic value for fluorine of 2.8 a
	www.chemistry.mcmaster.ca /esam/Chapter_7/intro.html (918 words)

	An Introduction to Ionic Compounds (Site not responding. Last check: 2007-10-10)
		The metallic radius becomes larger as we go down a column of the periodic table because the valence electrons are placed in larger orbitals.
		The metallic radius becomes smaller as we go from left to right across a row of the periodic table because the number of protons in the nucleus also increases as we go across a row of the table.
		The covalent radius of a chlorine atom, for example, is half the distance between the nuclei of the atoms in a Cl molecule.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch7/sizeframe.html (987 words)

	The first property to explore is atomic radius.
		To get the atomic radius we assume the distance between the two nuclei is the sum of two chlorine atomic radii.
		Therefore the atomic radius of chlorine is 0.994 Å.
		Another way to explain the trend in atomic radius across a period is in terms of the effective nuclear charge experienced by the valence electrons.
	intro.chem.okstate.edu /1314F00/Lecture/Chapter7/Lec111300.html (2187 words)

	Rationalization of 'Ionic' Structures
		The cation-anion distance is regarded as the sum of the ionic radii.
		Radius ratios might appear to work well for predicting structures of oxides, MO e.g.
		In a stable ionic structure the charge on an ion is balanced by the sum of electrostatic bond strengths to the ions in its coordination polyhedron
	www.chem.ox.ac.uk /icl/heyes/structure_of_solids/Lecture3/Lec3.html (1107 words)

	Chemical Sciences: Electronic Structure: Sizes of Atoms and Ions
		In this table the ionic radius given is the Pauling crystal radius.
		The atomic radii are always found to be larger than the ionic radii of the cations of the same atom because the electrons lost on ionization are the outermost electrons of the atom.
		The ionic radii of anions, however, are larger than the atomic radii because the added electron must go into the outermost orbital.
	www.psigate.ac.uk /newsite/reference/plambeck/chem1/p01231d.htm (204 words)

	Bonding in Materials (Site not responding. Last check: 2007-10-10)
		The coulombic nature of ionic interactions allows us to use a simple set of rules to determine the nature of packing in solids that are ionically bonded.
		Every charge-neutral atom has a characteristic radius that is determined by the size of its outer electron shells.
		Example: Neutral Cl atomic radius = 1.07 Å, but ionic radius of Cl When more than one possible ionization state exists, those with the higher negative charge are larger.
	www.mse.uiuc.edu /info/mse182/t81.html (280 words)

	General Chemistry Online: Glossary: The periodic table
		One half the distance between nuclei of atoms of the same element, when the atoms are bound by a single covalent bond or are in a metallic crystal.
		The radius of atoms obtained from covalent bond lengths is called the covalent radius; the radius from interatomic distances in metallic crystals is called the metallic radius.
		Elements that belong to the same group usually show chemical similarities, although the element at the top of the group is usually atypical.
	antoine.frostburg.edu /chem/senese/101/periodic/glossary.shtml (597 words)

	Crystallography : A Tutorial (Site not responding. Last check: 2007-10-10)
		the radius of the trivalent cation is smaller than that of the divalent cation, which is smaller than that of the monovalent cation
		It should be realized that the value of any ionic radius only serves as a useful but approximate size of the ion..
		The fact that the ionic radius of Na is 0.98Å does not mean that the electron cloud of the ion never extends beyond this value.
	www.keele.ac.uk /depts/ch/resources/xtal/types2.html (443 words)

	Chapter 12: Chemical bonding (Site not responding. Last check: 2007-10-10)
		Ionic bonds are formed by the transfer of electrons between atoms with a large difference in electronegativity.
		Ionic compounds are characterized by high melting points, solubility in water, and crystal formation.
		The ionic radius is the best estimate chemists can make of the effective size of an ion.
	home.earthlink.net /~gurkha711/Chem_Ch_12.htm (416 words)

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