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Topic: Lone pair

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	NPWRC :: Assessing Breeding Populations of Ducks by Ground Counts
		Because of poor visibility of pairs in the heavily vegetated parkland ponds, and because of the relatively large (10.5 square miles) study block in the grassland, two different census methods were adopted to assess the abundance of breeding pairs.
		Pair counts made on ponds in the western third of the study area showed that from 20 to 45 per cent of the pairs were flushed.
		Lone hens were not added to the population counts as I assumed all hens to be paired to one of the lone or grouped drakes already enumerated on the study block.
	www.npwrc.usgs.gov /resource/birds/duckcoun/census.htm (3141 words)

	curvedarrows.html (Site not responding. Last check: 2007-10-07)
		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.
		Lone pairs are often involved in reaction mechanisms, so you should be in the habit of drawing all lone pairs.
		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)

	lone pairs and dipole moments
		Lone pairs are not accounted for when determining dipole moments, dipole moments pertain to electronegativity, to the bonds involved since polarity pertains to when one element (locality) is electron deficient as a result of a stronger electronegative-neighbor element Relating to polarity.
		Well, firstly, the lone pair in the sp3 hybridized orbital of the nitrogen atom which is directed towards one end of the tetrahedral electron pair geometry of these molecules has a contribution to the dipole moment of the molecules.
		Saying that lone pairs contribute to the net dipole moment in that it contributes to the shape of the molecule is a bit of a stretch.
	www.physicsforums.com /showthread.php?p=251705 (1778 words)

	Lone Pairs and the Molecular Electrostatic Potential of Water
		Although the density is featureless, it is not spherical in the lone pair region.
		However, the slight asymmetry in the electron distribution, as shown in figure 3, is indeed consistent with the notion of lone pairs oriented approximately tetrahedrally with respect to the OH bonds.
		While the concept of a lone pair is extraordinarily valuable in interpreting, predicting and systematizing many aspects of chemistry, its characterization, as regions of space with significantly enhanced electron density is a considerable oversimplification.
	www.cem.msu.edu /~young/water/lp3.html (1694 words)

	ROCO Resonance: geometry
		4 pairs imply a tetrahedral atom with bond angles of ~109o, 3 pairs imply a trigonal atom with bond angles of 120o, and 2 pairs imply a linear atom.
		The counting of electron pairs, and the prediction of bond angles, becomes uncertain when a lone pair is delocalized.
		Any time a N (equipped with a lone pair) lies next to a pi system, it may be possible to delocalize the N lone pair by converting it into a pi bond pair.
	academic.reed.edu /chemistry/roco/Resonance/geometry.html (1324 words)

	Shapes of Molecules
		lone pair-lone pair repulsion is greater than bonding pair-bonding pair repulsion, so the lone pair pushes the bonding pairs closer together than in a tetrahedral arrangement of the 'electron clouds'.
		These lone pairs of electrons repel each other equally and will try to get as far away from each as possible.
		lone pair-lone pair repulsion is greater than lone pair-bonding pair or bonding pair-bonding pair repulsion, so the lone pairs of electrons push the bonding pairs of electrons closer together than in a tetrahedral arrangement of the 'electron clouds'.
	www.ausetute.com.au /shapemol.html (801 words)

	Chemistry 103A; Sections 5, 6, 7, 8; Lecture 1; 21 Aug 00
		The principal of VSEPR is that lone pairs and
		The lone pairs are not involved in a bond so that there in no second nucleus attached to a lone pair.
		Three pairs: the pairs are trigonal planer, the molecule may be trigonal planer or bent.
	www.chem.arizona.edu /~salzmanr/103a004/nts004/l29/l29.html (875 words)

	Chemical Mechanisms
		A lone pair from oxygen becomes shared with C to form a bond.
		Meanwhile the C has lost its share of the bonding pair, and unless this is replaced by incoming electrons, it becomes C+ with three bonds and an empty orbital.
		A bonding electron pair is lost from the H (becomes +1) and is transferred to the C. The central O keeps its share of the bond, so total bonds at the 'leapfrogged' O atom stay the same.
	www.chembio.uoguelph.ca /educmat/chm258/e-arrows.shtml (836 words)

	ROCO Curved Arrows: 3 possible changes
		The destination can be a lone pair (on A or B) or a bond (A-C or B-C), but it must involve A or B.
		Lone pairs can only change into bond pairs, but there are two ways to draw this.
		Bond pair to bond pair changes can also be drawn in two ways.
	academic.reed.edu /chemistry/roco/Arrows/curved_3kinds.html (744 words)

	Chapter Eleven: Molecular Shapes (Site not responding. Last check: 2007-10-07)
		In the theory, valence shell electron pairs are assumed to repel each other, assuming orientations to minimize repulsions and establish certain groups of molecular shapes.
		The reason for this is that lone pairs of electrons do not show up in the molecular configuration, although their effects are still seen (such as pushing bonding pair electrons closer together).
		Due to the greater repelling character of lone pairs, as also shown in the images above the H atoms are bent closer together than the regular tetrahedral angle of 109.5.
	www.chem.ufl.edu /~chm2040/Notes/Chapter_11/shapes.html (1374 words)

	Dictionary V (Site not responding. Last check: 2007-10-07)
		The valence shell electron pair repulsion theory explains the shapes of simple covalent molecules in terms of the interaction between the pairs of electrons in the valence shell of the central atom in the molecule.
		Lone pairs lie closer to the central atom than bond pairs, since the lone pairs have no other nearby positive nucleus to which they are attached to attract them away from the central atom.
		The presence of a lone pair in a molecule tends to cause the other bond pairs to move closer together.
	www.ucc.ie /ucc/depts/chem/dolchem/html/dict/000v1.html (925 words)

	VSEPR
		Recall that lone pairs occupy more angular space and are located closer to their atoms than bond pairs.
		The interaction between a lone pair and a bonding pair is somewhere in between.
		Since the lone pairs occupy a little more than their fair share of the available space, the effect is for the three Cl-F bonds to squeeze together slightly to make room for the lone pairs.
	winter.group.shef.ac.uk /vsepr/isomers.html (583 words)

	Lone pair - Wikipedia, the free encyclopedia (via CobWeb/3.1 planetlab1.tamu.edu) (Site not responding. Last check: 2007-10-07)
		A lone pair is an electron pair without bonding or sharing with other atoms.
		They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons.
		They can be identified by examining the outermost energy level of an electron--lone electron pairs consist of paired electrons as opposed to single electrons, which may appear if the atomic orbital is not full.
	en.wikipedia.org.cob-web.org:8888 /wiki/Lone_pair (217 words)

	Dipoles
		Lone pairs of electrons will almost always contain a larger partial negative charge than an atom.
		The greater partial negative is held by the lone pair of electrons, and thus the net dipole moment vector will point towards the lone pair of electrons.
		Thus, with the multiple dipole moments of each lone pair on the fluorines reducing the gross dipole moment provided by the fluorines --, and the comparison of hydridizations of nitrogen and the fluorines (when referring to their particular lone-pairs)
	www.physicsforums.com /showthread.php?t=95045 (960 words)

	intermolecular bonding - hydrogen bonds
		Lone pairs at the 2-level have the electrons contained in a relatively small volume of space which therefore has a high density of negative charge.
		Lone pairs at higher levels are more diffuse and not so attractive to positive things.
		The two strands of the famous double helix in DNA are held together by hydrogen bonds between hydrogen atoms attached to nitrogen on one strand, and lone pairs on another nitrogen or an oxygen on the other one.
	www.chemguide.co.uk /atoms/bonding/hbond.html (1200 words)

	co-ordinate (dative covalent) bonding
		Ammonium ions, NH, are formed by the transfer of a hydrogen ion from the hydrogen chloride to the lone pair of electrons on the ammonia molecule.
		) is transferred from the chlorine to one of the lone pairs on the oxygen atom.
		The lone pair on the nitrogen of an ammonia molecule can be used to overcome that deficiency, and a compound is formed involving a co-ordinate bond.
	www.chemguide.co.uk /atoms/bonding/dative.html (1434 words)

	VSEPR theory - Wikipedia, the free encyclopedia (via CobWeb/3.1 planetlab1.tamu.edu) (Site not responding. Last check: 2007-10-07)
		To achieve this, it is necessary to construct a valid Lewis structure that shows all of the bonds within the molecule and the locations of lone pairs of electrons.
		The lone pair-lone pair (lp-lp) repulsion is considered to be stronger than the lone pair-bonding pair (lp-bp) repulsion, which in turn is stronger than the bonding pair-bonding pair (bp-bp) repulsion.
		The ammonia molecule (NH) has three pairs of electrons involved in bonding, but there is a lone pair of electrons on the nitrogen atom.
	en.wikipedia.org.cob-web.org:8888 /wiki/VSEPR (614 words)

	Trigonal Pyramid Geometry
		An example of trigonal pyramid molecular geometry that results from tetrahedral electron pair geometry is NH The nitrogen has 5 valence electrons and thus needs 3 more electrons from 3 hydrogen atoms to complete its octet.
		The molecule is trigonal pyramid molecular geometry because the lone electron pair, although still exerting its influence, is invisible when looking at molecular geometry.
		The molecule is three dimensional as opposed to the boron hydride case which was a flat trigonal planar molecular geometry because it did not have a lone electron pair.
	www.elmhurst.edu /~chm/vchembook/205trigpyramid.html (338 words)

	Water molecule structure
		In a perfect tetrahedral arrangement the bond-bond, bond-lone pair and lone pair-lone pair angles would all be 109.47° and such tetrahedral bonding patterns are found in condensed phases such as hexagonal ice.
		Early 5-point molecular models, with explicit negative charge where the lone pairs are purported to be, faired poorly in describing hydrogen bonding, but a recent TIP5P model shows some promise.
		Although the lone pairs of electrons do not appear to give distinct directed electron density in isolated molecules, there are minima in the electrostatic potential in approximately the expected positions.
	www.lsbu.ac.uk /water/molecule.html (1614 words)

	Drawing Lewis Structures
		Connect each contiguous pair of atoms with one of the VSE pairs; each Bond Pair is shown as a line.
		Push a lone pair on any of the three O into bonding position, creating one C-O double bond.
		Assign both electrons of a lone pair to the valence shell of the atom.
	wb.chem.lsu.edu /htdocs/people/sfwatkins/MERLOT/drawlewis/dls.html (1604 words)

	Chemistry 103A; Sections 5, 6, 7, 8; Lecture 1; 21 Aug 00
		-bonded pairs around a nucleus is determined simply by the pairs trying to reduce crowding.
		That is, the pairs try to get as far away from each other as they can.
		Five pairs: the electron pairs are pointing toward the corners of a regular trigonal bipyramid.
	www.chem.arizona.edu /~salzmanr/103a004/nts004/l30/l30.html (529 words)

	CHEMystery: Atomic Structure and Bonding: Predicting the Shapes of Molecules
		It is based on the idea that valence shell electron pairs want to stay as far apart from each other as possible (because they are negatively charged) so that their repulsions are at a mininium.
		But since one of the pairs are lone, you take one vertex off of the planar triangular.
		For five valence pairs, the axial bonds are not removed because they have a larger bond angle from each other, 180°.
	library.thinkquest.org /3659/structures/predict.html (459 words)

	Lone Pair Effect in Thallium(I) Macrocyclic Compounds (Site not responding. Last check: 2007-10-07)
		The role of the inert (lone) pair of electrons in thallium(I) salts is studied by comparison of the compounds [Tl@18-crown-6]
		In contrast to common introductory chemistry textbook opinions, the paradigm that s-p hybridization is a prerequisite for an inert electron pair to become stereochemically active in compounds of the heavier main group elements has to be revised.
		Instead, an inert pair of electrons is expected to become stereochemically involved whenever it is forced to participate in antibonding orbital interactions with its surroundings, and there is the possibility for a structural distortion that minimizes these repulsive forces.
	pubs.acs.org /cgi-bin/abstract.cgi/inocaj/2005/44/i18/abs/ic050547k.html (184 words)

	ILL : ANNUAL REPORT 2000
		It is well known and documented that electronic lone pairs, whatever the electronic shell, have a spatial extension close to that of an oxide ion, thus distorting the ligands environment of the cation [6].
		without any lone pair creates two vacancies in place of the lone pairs, half of which being occupied by the extra oxygen atom necessary to fulfil the lanthanum valence.
		Such an approach [7], called the LPS (for Lone Pair Substitution) concept can be applied to a variety of already known oxides of lone-pair elements (such as In, Ge Sb, Se, among others).
	www.ill.fr /AR-00/p-38.htm (1040 words)

	VSPER
		The chief tenet of the theory is that electron groups (either lone pairs or bonding pairs of electrons) will try to maximize the distance between themselves and minimize repulsions between electron pairs.
		Doing so leads to the formation of 5 primary electron group geometries which the molecular structures of the molecules are based on.
		Lone pairs require more room and will force atoms (bonding pairs) closer together than expected based upon the electron group geometry
	webhost.bridgew.edu /shaefner/general/vsepr.html (262 words)

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