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	Molecular orbital - Wikipedia, the free encyclopedia
		For an imprecise, but qualitatively useful, discussion of the molecular structure, the molecular orbitals can be obtained from the "Linear combination of atomic orbitals molecular orbital method" ansatz (using eventually the concept of hybridized orbitals).
		The linear combination of atomic orbitals approximation for molecular orbitals was introduced in 1929 by Sir John Lennard-Jones.
		To obtain quantitative values for the molecular energy levels, one needs to have molecular orbitals which are such that the configuration interaction (CI) expansion converges fast towards the full CI limit.
	en.wikipedia.org /wiki/Molecular_orbital (848 words)

	Molecular Orbital Theory (Site not responding. Last check: 2007-10-24)
		Molecular orbital theory is more powerful than valence-bond theory because the orbitals reflect the geometry of the molecule to which they are applied.
		Molecular orbitals are obtained by combining the atomic orbitals on the atoms in the molecule.
		To sort out the relative energies of the six molecular orbitals formed when the 2p atomic orbitals on a pair of atoms are combined, we need to understand the relationship between the strength of the interaction between a pair of orbitals and the relative energies of the molecular orbitals they form.
	chemed.chem.purdue.edu /genchem/topicreview/bp/ch8/mo.html (1304 words)

	Molecular Orbital Theory
		MO Theory- Molecular Orbital Theory describes covalent bonds in terms of molecular orbitals, which result from interaction of the atomic orbitals of the bonding atoms and are associated with the entire molecule.
		A bonding molecular orbital has lower energy and greater stability than the atomic orbitals from which it was formed.
		An antibonding molecular orbital has higher energy and lower stability than the atomic orbitals from which it was formed.
	www.molecularsoft.com /data/help/Chemical_Bonds-MO.htm (256 words)

	BBC - h2g2 - Molecular Orbital Theory of Chemical Bonding
		Molecular orbital [MO] theory is a more developed and accurate theory for chemical bonding than valence bond [VB] theory and is used almost universally in theoretical and computational chemistry.
		Antibonding orbitals are often more antibonding than the bonding orbitals are bonding (ie, the energy gap upwards from the atomic orbitals to the antibonding orbital is greater than the drop down from the atomic orbitals to the bonding orbital).
		The participating orbital on fluorine is at lower energy to the hydrogen s-orbital and is therefore closer the energy of the 1σ orbital.
	www.bbc.co.uk /dna/h2g2/A1011899 (3087 words)

	HighBeam Encyclopedia - molecular orbital theory
		MOLECULAR ORBITAL THEORY [molecular orbital theory] detailed explanation of how electrons are distributed in stable molecules.
		In the simpler valence theory of the chemical bond, each atom in a molecule is assumed to retain its own electrons.
		Each orbital can hold a maximum of two valence electrons and the structure of the molecule is built up by filling the lowest energy orbitals first.
	www.encyclopedia.com /html/m1/molecorb.asp (306 words)

	C05-1-2-6-0-0-0:Molecular orbital theory (Site not responding. Last check: 2007-10-24)
		Molecular orbital theory (MO Theory) is based upon the notion that molecular orbitals are formed from a collection of atomic orbitals within a molecule.
		Of the two molecular orbitals produced from two atomic orbitals, one is a bonding orbital (lower energy) and one is an anti-bonding orbital (higher energy).
		Molecular orbitals that are lower in energy than the original atomic orbitals that produced them are termed bonding molecular orbitals.
	dwb.unl.edu /Teacher/NSF/C05/C05Mats/MOTheory.html (387 words)

	Molecular Orbital Theory (Site not responding. Last check: 2007-10-24)
		The goal of molecular orbital theory is to describe molecules in a similar way to how we describe atoms, that is, in terms of orbitals, orbital diagrams, and electron configurations.
		Molecular orbitals are formed from the overlap of atomic orbitals.
		Because electrons in the molecular orbital are lower potential energy than in separate atomic orbitals, energy would be required to shift the electrons back into the 1s orbitals of separate atoms.
	www.mpcfaculty.net /mark_bishop/molecular_orbital_theory.htm (1632 words)

	Molecular Orbital Diagrams (Site not responding. Last check: 2007-10-24)
		The interactions of the atomic orbitals to form molecular orbitals is represented by an energy diagram called a molecular orbital diagram.
		The dotted lines are used to connect molecular orbitals with the atomic orbitals that "mixed" to form the molecular orbital.
		The lower energy orbital is the bonding orbital; the higher energy orbital is the anti-bonding orbital.
	www.chm.davidson.edu /ChemistryApplets/MolecularOrbitals/MO.html (507 words)

	SparkNotes: Organic Molecular Orbitals: Molecular Orbital Theory
		Valence Bond theory, as we saw in the last section, is based on the notion that electrons are localized to specific atomic orbitals.
		Molecular orbital theory holds, as its name suggests, that electrons reside in molecular orbitals that are distributed over the entire molecule.
		Antibonding orbitals are denoted with an asterisk (*).
	www.sparknotes.com /chemistry/organic1/orbitals/section2.rhtml (892 words)

	Intute sciences - Chemical Sciences: Introduction to Molecular Orbitals
		The molecular orbital approach, at the qualitative and descriptive level at which we shall introduce it, is useful primarily as a method of determining energy levels in molecules and the distribution of electrons among these energy levels.
		The principle of the molecular orbital theory is that the electronic structures of molecules are determined primarily by the nuclei of the atoms which constitute them and the arrangement of those nuclei in space.
		As a consequence the electrons in the molecule will prefer to occupy the bonding molecular orbital and the difference in energy between the bonding molecular orbital and the two original atomic orbitals is the bond enthalpy of the hydrogen molecule.
	www.intute.ac.uk /sciences/reference/plambeck/chem1/p02211.htm (1024 words)

	Molecular Orbitals - Introduction
		For example, the 2s orbital in the lithium atom is a function which determines the motion of an electron in the potential field of the nucleus and in the average field of the two electrons in the 1s orbital.
		Once the forms and properties of the molecular orbitals are known, the electronic configuration and properties of the molecule are again determined by assigning electrons to the molecular orbitals in the order of increasing energy and in accordance with the Pauli exclusion principle.
		In molecular orbital theory the bond is described in terms of a single orbital which is determined by the field of both nuclei.
	www.chemistry.mcmaster.ca /esam/Chapter_8/intro.html (541 words)

	Molecular modeling - MO theory (Site not responding. Last check: 2007-10-24)
		Half of the molecular orbitals are bonding and have a lower energy than the isolated p atomic orbitals from which they are comprised, and the other half are antibonding MOs and are higher in energy.
		The presence of alkyl substituents does not alter the MO structure, e.g., the organization of MOs in the orbital diagram of 1,3 butadiene is similar to that of 1,3 pentadiene.
		Orbitals such as the HOMO and LUMO are referred to as frontier orbitals, and are important because most chemical reactions involve electron movement between them.
	departments.oxy.edu /chemistry/wreef/Spring_MO.html (1578 words)

	Organic Chemistry at Penn State: Quantum Primer III (Site not responding. Last check: 2007-10-24)
		All atoms in the molecule provide their atomic orbitals for construction of MO, but not all atomic orbitals must participate in all MO. The number of MO is equal to the number of atomic orbitals used to generate them.
		We have to use each atomic orbital completely, we have to generate normalized molecular orbitals (MOs), and the number of MOs must be equal to the number of atomic orbitals that we have started with.
		The usual energy order of MO is as follows: σ-type orbitals (the lowest energy), π-type orbitals, n-type orbitals (nonbonding, such as lone pairs), π-type orbitals* and σ-type orbitals* (the highest in energy).
	courses.chem.psu.edu /chem38/quantum/quantum3.html (1337 words)

	Molecular Orbital Bonding (Site not responding. Last check: 2007-10-24)
		However, since no more than two electrons can be in any orbital, whether it be an atomic orbital or a molecular orbital, the other two electrons must be in a higher energy molecular orbital.
		Molecular orbital theory tells us that when atoms come together their atomic orbitals overlap.
		The number of molecular orbitals is always the same as the number of atomic orbitals they came from.
	people.depauw.edu /jhansen/Chem120S04/MObonding.html (380 words)

	Introduction to Molecular Orbital Theory
		There are two molecular orbitals for hydrogen, the lower energy orbital has its greater electron density between the two nuclei.
		The upper molecular orbital has a node in the electronic wave function and the electron density is low between the two positively charged nuclei.
		The energy of the upper orbital is greater than that of the 1s atomic orbital, and such an orbital is called an antibonding molecular orbital.
	www.ch.ic.ac.uk /vchemlib/course/mo_theory/main.html (2412 words)

	SparkNotes: Molecular Orbitals: Molecular Orbital Theory
		Molecular orbital theory posits the notion that electrons in molecules likewise exist in different orbitals that give the probability of finding the electron at particular points around the molecule.
		Notice that the orbitals of the separated atoms are written on either side of the diagram as horizontal lines at heights denoting their relative energies.
		From the orbital correlation diagram above you should notice that the amount of stabilization due to bonding is equal to the amount of destabilization due to antibonding, because there are two electrons in the bonding orbital and two electrons in the antibonding orbital.
	www.sparknotes.com /chemistry/bonding/molecularorbital/section1.html (1814 words)

	Chemistry : Chapter 6 : Molecular Orbital Theory
		That is, s orbitals with s orbitals and the p orbitals with p orbitals of the same orientation.
		It is traditional to graph the energy of the molecular orbitals in comparison to the atomic orbitals.
		One of those molecular orbitals will be lower in energy than the atomic orbitals (bonding orbital) One will be higher in energy than the atomic orbitals (antibonding orbital).
	www.wwnorton.com /internal/chem/concepts/chapter6/ch6_3.htm (365 words)

	Sinanoglu, Oktay - Book: Sigma Molecular Orbital Theory (1970) - Component of : Early Ideas in the History of Quantum ...
		As in pi-electron theory, semiempirical sigma MO methods have been used by and large for charge distributions, dipole moments, and conclusions that can be drawn from chargc distributions, such as die inductive effects of substituents and reactivity of sites.
		A framework for molecular orbitals is provided by die Hartree-Fock method, which yields the best single determinantal wave function made up of spin orbitals, each detersnined in the SCF of all the electrons in the system.
		It is also well known that in the orbital theory itself one needs to minimize the energy of each state separately to obtain orbitals appropriate to that state.
	www.quantum-chemistry-history.com /Sina_Dat/BOOKSiMolOrb/SiMol1.htm (3788 words)

	Molecular Orbital Theory. (Site not responding. Last check: 2007-10-24)
		Basically, in a molecule, all the atomic orbitals interact in such a way that they become new “Molecular orbitals” that encompass (or can encompass) the entire molecule.
		Molecular Orbital : results from the interaction of the atomic orbitals of the bonding atoms and are associated with the entire molecule.
		With Molecular orbital theory, we think of say, a 2s orbital on one atom and a 2s orbital on another atom forming a sigma (_) bonding orbital which is part of the molecule and doesn’t belong to either of the atoms.
	www.ndsu.nodak.edu /ndsu/joeaton/chem121/chap10/Chapter10lecture3/tsld003.htm (120 words)

	G.G. Hall about Lennard-Jones, Sir John Edward - concerning : Early Ideas in the History of Quantum Chemistry.
		Thus his first approximation to the molecular orbital is a linear combination of H-like atomic orbitals suitably normalized using the overlap integral.
		The first accurate calculation of a molecular orbital wavefunction was the Coulson (11) calculation on the hydrogen molecule.
		His molecular structure work is represented in a relatively small number of papers but shows him trying to understand the fundamental aspects of the subject and injecting ideas which we still find useful.
	www.quantum-chemistry-history.com /LeJo_Dat/LJ-Hall1.htm (1553 words)

	BBC - h2g2 - Molecular Orbital Theory of Chemical Bonding.
		Molecular orbital (MO) theory is a more developed and accurate theory for chemical bonding than valence bond theory and is used almost universally in theoretical and computational chemistry.
		The 6 π electrons fill the highly bonding and the two slightly bonding molecular orbitals, all of which are at lower energy than the p-orbitals of the separated atoms.
		Molecular orbital theory provides a quntitative model for the chemical bonding in virtually all types of compound from simple diatomic molecules to more complex organic and inorganic compounds to large metal clusters.
	www.bbc.co.uk /dna/ww2/A986835 (3097 words)

	Grandinetti (Site not responding. Last check: 2007-10-24)
		In Molecular Orbital Theory we view the bonding of the two H-atoms as partial constructive interference between standing wavefunctions of the 1s orbitals.
		When atomic orbitals are combined to give molecular orbitals, the number of molecular orbitals formed equals the number of atomic orbitals used.
		In general, the energy difference between a bonding and anti-bonding orbital pair becomes larger as the overlap of the atomic orbitals increase.
	www.chemistry.ohio-state.edu /~grandinetti/teaching/Chem121/lectures/MOTheory/MOTheory.html (526 words)

	Erik's Chemistry: Molecular Orbital Theory: HOMO and LUMO
		These orbitals are called the frontier orbitals, and determine the way the molecule interacts with other species.
		The HOMO is the orbital that could act as an electron donor, since it is the outermost(highest energy) orbital containing electrons.
		The LUMO is the orbital that could act as the electron acceptor, since it is the innermost(lowest energy) orbital that has room to accept electrons.
	eppe.tripod.com /homolumo.htm (328 words)

	Molecular orbitals
		Many models and theories have been proposed to explain the chemical bond, and here are some simplified forms of these theories, some of which may have been proposed as the society began to speculate what is happening.
		Molecular orbital (MO) theory suggested atomic orbitals which not only overlap, but are simultaneously transformed into molecular orbitals with new energies and new electron distributions.
		The molecular orbital approach is one explanation for the H-H bond.
	www.science.uwaterloo.ca /~cchieh/cact/c120/mo.html (743 words)

	Discussion of molecular orbital theory
		Molecular Orbital theory attempts to determine the values of the wavefunction for electrons that are bound to a molecular framework.
		Almost all MO (molecular orbital) calculations rely on the Born-Oppenheimer approximation: since the nuclei are at least 1000 times more massive than the electrons, they are relatively motionless on the timescale of electron motion.
		This simplifies the calculations immensely and also allows for a very simplistic approximation that ignores certain aspects of the differential equations involved, but is still reasonably accurate, and is (most notably) very simple to implement, and this is the strategy that I have chosen to implement.
	archive.ncsa.uiuc.edu /Classes/MATH198/kaduk/discussion.html (225 words)

	Molecular Orbitals (Site not responding. Last check: 2007-10-24)
		Molecular orbitals are of course familiar to you already - you have discussed them in all sort of courses you have already followed.
		Molecular orbitals must belong to one of the irreducible representations (irreps) of the molecular Point Group.
		Building up the molecular orbitals of large molecules directly from atomic orbitals is hard to do in the same qualitative way we have used above, because there are so many orbitals to consider.
	www.chm.bris.ac.uk /pt/harvey/elstruct/lcao_mo.html (2100 words)

	HOMO/LUMO - Wikipedia, the free encyclopedia
		HOMO and LUMO are acronyms for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively.
		The difference of the energies of the HOMO and LUMO, termed the HOMO/LUMO gap can sometimes serve as a measure of the excitability of the molecule: the smaller the energy, the easier it will be excited.
		When the molecule forms a dimer or an aggregate, the proximity of the orbitals of the different molecules induce a splitting of the HOMO and LUMO energy levels.
	en.wikipedia.org /wiki/HOMO (256 words)

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