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Topic: Electron pair

	Electron pair geometry (Site not responding. Last check: 2007-10-26)
		The geometry is determined by minimizing the repulsions between electron pairs in the bonds between atoms and/or lone pairs of electrons as postulated by VSEPR theory.
		Electron pairs are defined as electrons in bonds, lone pairs, and occasionally a single unpaired electron.
		In methane, ammonia, water and hydrogen fluoride, the electron pair geometry is tetrahedral.
	www.elmhurst.edu /~chm/vchembook/207epgeom.html (257 words)

	Covalent Bonding and Electron Pair Sharing
		These electrons can be effectively partitioned into a core and a valence shell, and it is only the electrons in the valence shell which are significant to the chemical properties of the atom.
		We thus extend our model of valence shell electron pair sharing to conclude that carbon atoms can bond by sharing one, two, or three pairs of electrons as needed to complete an octet of electrons, and that the strength of the bond is greater when more pairs of electrons are shared.
		Pairing the two non-bonding electrons seems reasonable in analogy to the fact that electrons are paired in forming covalent bonds.
	cnx.org /content/m12584/latest (4673 words)

	curvedarrows.html
		Electrons never flow from atoms which are electron-poor to atoms which are electron-rich, so a curved arrow will never point from an atom with a positive charge to an atom with a negative charge.
		The curved arrow on the left indicates the electron pair that was the O-H bond becomes a lone pair on the oxygen of the hydroxide ion.
		The curved arrow on the right indicates that the electron pair of the bromine-bromine bond is shifting to reside solely on the bromine on the right, resulting in rupture of the bond and formation of bromine with four lone pairs and a negative charge.
	web.chem.ucla.edu /~harding/tutorials/curvedarrows/curvedarrows.html (1233 words)

	Leptons
		As one of the leptons, the electron is viewed as one of the fundamental particles.
		Associated with the electron is a the electron neutrino.
		When a photon has quantum energy higher than the rest mass energy of an electron plus a positron, one of the ways that such a photon interacts with matter is by producing and electron-positron pair.
	hyperphysics.phy-astr.gsu.edu /hbase/particles/lepton.html (635 words)

	Valence Shell Electron Pair Repulsion Theory (Site not responding. Last check: 2007-10-26)
		It is to use this distribution of electrons to predict the shape of the molecule.
		Nonbonding electrons need to be close to only one nucleus, and there is a considerable amount of space in which nonbonding electrons can reside and still be near the nucleus of the atom.
		The force of repulsion between a pair of nonbonding electrons and a pair of bonding electrons is somewhat smaller, and the repulsion between pairs of bonding electrons is even smaller.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch8/vsepr.php (1344 words)

	Chemistry Configuration Electron (Site not responding. Last check: 2007-10-26)
		While most electrons are found in atoms, others move independently in matter, or the late 1890s a number of physicists posited that electricity could be electrons than protons, the object is said to be positively charged.
		Of course, this number is even move in Cooper pairs, in which their motion is coupled to nearby matter via The electron is an elementary particle — it has no substructure (at least, that one could infer from its charge if the physics were only described by the electron to roughly 51 GeV.
		The discovery that the electron was a subatomic particle was made in 1897 by along its spin axis.
	doppler.boekebeurs.be /Electron/chemistry-configuration-electron.php (939 words)

	Chapter 9: Molecular Geometry and Bonding Theories
		In an equatorial position, an electron pairs is situated 120° from the other two equatorial pairs and 90° from the two axial pairs.
		least one pair of electrons is localized in the space between the atoms, in a σ bond.
		Because it concentrates electron density between both nuclei, the bonding molecular orbital holds the atoms together in a covalent bond.
	www.geocities.com /wh0ami5/htmlnotes/ch9notes.htm (3022 words)

	Bent Molecular Geometry (Site not responding. Last check: 2007-10-26)
		The water molecule is bent molecular geometry because the lone electron pairs, although still exerting influence on the shape, are invisible when looking at molecular geometry.
		The molecule is two dimensional and bent as opposed to the beryllium hydride case which was a linear or straight line molecular geometry because it did not have a lone electron pair.
		The nitrogen and and one oxygen are bonded through a double bond which counts as "one electron pair".
	www.elmhurst.edu /~chm/vchembook/206bent.html (429 words)

	test (Site not responding. Last check: 2007-10-26)
		The electron shell repulsion between these four electron pairs is minimized in a tetrahedral arrangement (i.e.
		Since the electron pairs of bonding atoms are somewhat delocalized from the individual atoms (i.e.
		they are shared by two atoms), whereas the nonbonding electron pairs are attracted to a single nucleus, the nonbonding pairs can be thought of as having a somewhat larger electron cloud near the parent atom (kind of like being a somewhat larger balloon in the balloon analogy).
	wine1.sb.fsu.edu /chm1045/notes/Geometry/VSEPR/Geom02.htm (681 words)

	The use of curly arrows to show electron movements in reaction mechanisms
		That's always fairly obvious, but you must show the electron pair either as a bond or, if it is a lone pair, as a pair of dots.
		Remember that a lone pair is a pair of electrons at the bonding level which isn't currently being used to join on to anything else.
		Notice also that the electron movement between the H and Br is shown as a curly arrow even though the electron pair moves straight down.
	www.chemguide.co.uk /basicorg/conventions/curlies.html (790 words)

	vgn-ext-hidden_PubMed (Site not responding. Last check: 2007-10-26)
		We show that the concept of the electron pair bond has endured to the present day and is now understood to be a consequence of the Pauli principle.
		Today it is realized that bonding electron pairs in many molecules are not as well localized as Lewis believed, nevertheless resonance structures, i.e., plausible alternative Lewis structures, are still often used to describe such molecules.
		The electron density distribution in a molecule can now be analyzed using the ELF and other functions of the electron density to show where electron pairs are most probably to be found in a molecule.
	www.plwc.org /portal/site/ASCO/menuitem.a3fb42726842a82627c4c291ee37a01d/?vgnextoid=d70b3608f9958010VgnVCM100000f2730ad1RCRD&index=n&pmid=17109437 (334 words)

	Valence Shell Electron Pair Repulsion Theory
		In this model, the electrons being shared by the central nitrogen and the fluorine atoms are represented by the single bonds.
		Adding the paired but unshared electrons from the nitrogen, the non-bonding pair, and also the faces of the pyramid formed by allowing the three fluorine atoms and the non-bonding pair to form the four vertices of the pyramid, the geometry of the nitrogen trifluoride molecule is shown to be trigonal pyramidal.
		There is a simple way to predict molecular geometries by counting the numbers of bonding pairs of electrons and the numbers of non~bonding pairs of electron but first we need to look all of the possible geometries.
	www.chemvc.com /~tim/VSEPR.html (283 words)

	Electrons
		In laboratory experiments these particles were directed by electrically charged structures (similar to the "electron guns" inside TV picture tubes) to form beams.
		From such experiments and others the mass of the emitted particles, which became known as "electrons", could be determined.
		Sunlight knocks out electrons from the surface and a few manage to escape, leaving the spacecraft positively charged; the situation then stabilizes, because the positive charge prevents any more electrons from leaving.
	www-istp.gsfc.nasa.gov /Education/welect.html (458 words)

	Example Electron Pair Events (Site not responding. Last check: 2007-10-26)
		Events in which an electron-positron pair are produced are fairly easy to identify.
		We see a back-to-back pair of high momentum tracks pointing at high energy clusters of energy in the electromagnetic calorimeter.
		In the second example event the electrons strike the end-cap region of the detector.
	www.hep.man.ac.uk /u/summer/chee.html (47 words)

	Valence Shell Electron Pair Repulsion model
		The Valence Shell Electron Pair Repulsion (VSEPR) model for molecular bonding is discussed in the text in Section 3.6 starting on page 80.
		Once you have closen your molecule, move to the Electrons tab and count the number of valence electrons in your chosen molecule.
		The Geometry tab lets you select electron pair and molecular geometries, name them, decide about the molecule's net dipole moment, and check all your selections.
	www.dartmouth.edu /~genchem/0102/spring/vsepr.html (295 words)

	Atomic Orbitals
		Electron orbitals are the probability distribution of an electron in a atom or molecule.
		The electron orbitals presented here represent a volume of space within which an electron would have a certain probability of being based on particular energy states and atoms.
		For example, in a simple lowest-energy state hydrogen atom, the electrons are most likely to be found within a sphere around the nucleus of an atom.
	orbitals.com /orb (422 words)

	Shapes of molecules and bond angles at Doc Brown's Chemistry Clinic. Electron pair repulsion theory learn learning ...
		The shape of a molecule is determined by the number of groups of electrons around the central atom.
		The 'groups' might be a non-bonding single electron, a non-bonding or bonding pair of electrons, a double pair of bonding electrons or triple pair of bonding electrons etc. The electron 'groupings' repel to minimise the potential energy of the system i.e.
		Any lone pairs of non-bonding electrons on the central atom X, are closer to X than bond pairs because there is no Q atom attracting/sharing the lone pair electron charge.
	www.wpbschoolhouse.btinternet.co.uk /page06/molecule_shapes.htm (1256 words)

	Valence Shell Electron Pair Repulsion Models
		However, the Lewis dot structure for them are different, and the electron pair in :PF is the reason for its structure being different from BF (no lone pair).
		The Valence-Shell Electron-Pair Repulsion (VSEPR) models consider the unshared pairs (or lone electron pairs) and the bonding electrons.
		If the lone electron pairs are ignored, the geometry of the molecule is given by another descriptor.
	www.science.uwaterloo.ca /~cchieh/cact/c120/vsepr.html (885 words)

	Valence Shell Electron Pair Repulsion Theory (Site not responding. Last check: 2007-10-26)
		VSEPR introduces the rules for using valence shell electron pair repulsion theory to predict the shapes of simple molecules.
		First, the five spatial arrangements that accommodate symmetric distributions of from two to six pairs of electrons with minimum repulsion are shown in three dimensions.
		VSEPR Quiz allows students to practice identifying the correct arrangements of electron pairs surrounding a central atom, and, based on these arrangements, to predict the actual geometric shapes of simple molecules.
	www.cem.msu.edu /~gencem/vsepr (199 words)

	Valence Shell Electron Pair Repulsion
		Valence shell electron pair repulsion theory, VSEPR, is a super-simple technique for predicting the shape or geometry of atomic centres in small molecules and molecular ions:
		the overall geometry of the atomic centre is determined by the mutual repulsion between the electron pairs of the total coordination number.
		Lone pairs of electrons (nonbonded pairs) are taken into account in determining the total coordination number and VSEPR geometry, but they are NOT used when defining the geometry of an atomic centre, only the atoms are used:
	www.chemistry-drills.com /VSEPR.php (754 words)

	electron pair: definition, usage and pronunciation - YourDictionary.com (Site not responding. Last check: 2007-10-26)
		electron pair: definition, usage and pronunciation - YourDictionary.com
		Two electrons functioning or regarded as functioning in concert, especially two electrons that form a nonpolar covalent bond between atoms.
		The combination of an electron and a positron as produced by a high-energy photon.
	www.yourdictionary.com /ahd/e/e0080000.html (42 words)

	Chemical Sciences: Valence Shell Electron Pair Repulsion: Distortions (Site not responding. Last check: 2007-10-26)
		The effect of this repulsion will be to move the substituents closer to each other, and farther away from any unshared electron pairs, than they would be found in the basic structure.
		It is possible for a single atom, particularly an atom of oxygen or sulfur, to share two of the electron pairs on a neutral atom rather than one.
		The two electron pairs shared must occupy roughly the smae space, the space between the two atoms to which they are bound, and so the two bonding pairs act as if they were a single electron pair in establishing the basic molecular geometry.
	www.ualberta.ca /~jplambec/che/p101/p01252.htm (189 words)

	One Non-Bonding Electron Pair (Site not responding. Last check: 2007-10-26)
		This would force the bonding pairs to form a tri-pod arrangement which is referred to as a Trigonal Pyramidal geometry with a 107 degree separation of the bonding pairs from one another..
		One could place four of the bonding pairs in the same plane forming a square and the fifth bonding pair would be either above or below that plane.
		An example of this profile would be IF Then there are molecular systems that have two non-bonding electron pairs on the central atom.
	members.aol.com /profchm/one_nb.html (350 words)

	Systematic study of low-mass electron pair production in p--Be and p--Au collisions at 450 - Collaboration, of, ...
		In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p--Be and p--Au collisions at 450 GeV/c at the CERN SPS.
		In the range covered up to ß 1.5 GeV/c 2 the mass spectra from p--Be and p--Au collisions are well explained by electron pairs from decays of neutral mesons.
		For p--Be, the simultaneously measured electron pairs and photons served as a direct measure of the j Dalitz decay contribution to the inclusive pair...
	citeseer.ist.psu.edu /40026.html (598 words)

	The Electron-Pair wavefunction
		Because of the correlation of the electron pairs, it is highly improbable that once the superconducting state has been entered, a pair will be scattered out of the flow (i.e.
		cause resistivity), since this would imply that all the electron pairs have to change their states.
		The wavefunctions of the electron-pairs are correlated by with the other pairs by a phase difference, meaning that the knowledge of the wavefunction at one place determines it at another.
	www.maths.tcd.ie /~baz/squid/node4.html (217 words)

	Sizzling Organic Chemistry Dramas
		Electrons were drawn on posterboard and exchanged where appropriate.
		Here, you let me hold most of these electrons while I stand out of sight behind you and you pretend to be a cation.
		Just grab a pair of my electrons and let go of my Twin's electrons at the same time, and you'll be okay.
	www.heptune.com /chemtale.html (2109 words)

	OUP: UK General Catalogue
		Particular emphasis is placed on the valence-shell electron pair (VSEPR) and ligand close packing (LCP) models as well as the analysis of electron density distributions by the atoms in molecules (AIM) theory.
		Written by one the world's foremost authorities on the chemical bond, this textbook is ideal for courses on chemical bonding in chemistry departmetns at the senior/first year graduate level and can also be used to supplement inorganic survey courses needing an increased focus on bonding.
		It provides undergraduate (and 1st year graduate) students with an introduction to models and theories of chemical bonding and geometry as applied to the molecules of the main group elements.
	www.oup.com /uk/catalogue/?ci=0-19-510496-X (823 words)

	Valence Shell Electron Pair Repulsion Model (Site not responding. Last check: 2007-10-26)
		Another assumption is that lone bonding pairs tend to assume more s character (which means that they use up a greater angular volume than bp.
		The most electronegative F attracts the bonding pair away from the central P and allows the lp to expand while the F—P—F angle closes.
		A lone pair can thus be regarded as a bonding pair where the substituent has no electronegativity at all and thus the lp is diffuse around the central ion.
	www.unine.ch /chim/chw/VSEPR.html (515 words)

	VSEPR in TutorGig Tutorials
		determine the total number of valence electrons in the compound ___________________ 2.
		pairs in the valence shell of an atom to the geometrical arrangement of electron pairs (vsepr...
		: vsepr model and bond angles electron pair geometry and molecular geometry axial and equatorial lone...
	www.tutorgig.com /t/VSEPR (448 words)

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