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A Brief Introduction to Molecular Orbital Theory
A Brief Introduction to Molecular Orbital Theory
Published: 2013/04/16
Channel: ChemSurvival
The Molecular Shape of You (Ed Sheeran Parody) | A Capella Science
The Molecular Shape of You (Ed Sheeran Parody) | A Capella Science
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Orbital Molecular Theory
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14.2 Describe σ and π bonds IB Chemistry [HL IB Chemistry]
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chemistry: shape of orbitals (Techclass Animation)
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atomic d orbitals
atomic d orbitals
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Electron Orbitals - s,p & d
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s and p orbitals, orbitais s e p
s and p orbitals, orbitais s e p
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Hybrid Orbitals explained - Valence Bond Theory | Crash Chemistry Academy
Hybrid Orbitals explained - Valence Bond Theory | Crash Chemistry Academy
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Orbitals: Crash Course Chemistry #25
Orbitals: Crash Course Chemistry #25
Published: 2013/08/05
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Molecular Orbital Theory Chemistry
Molecular Orbital Theory Chemistry
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Introduction to the Molecular Orbitals of Conjugated Alkenes
Introduction to the Molecular Orbitals of Conjugated Alkenes
Published: 2013/04/15
Channel: ChemSurvival
Balloons, Hybrid Orbitals and Multiple Bonds
Balloons, Hybrid Orbitals and Multiple Bonds
Published: 2012/12/18
Channel: FlinnScientific
Resonance in Benzene
Resonance in Benzene
Published: 2010/11/30
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Molecular Orbital Theory
Molecular Orbital Theory
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Channel: Soumitra Das
Hybrid Orbital Formation
Hybrid Orbital Formation
Published: 2008/10/21
Channel: mtchemers
Sigma and Pi bonds
Sigma and Pi bonds
Published: 2014/05/06
Channel: 7activestudio
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Valence Bond Theory, Hybrid Orbitals, and Molecular Orbital Theory
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Channel: Professor Dave Explains
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Hybridization Theory
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STD 11 (Chemistry) - Hybridization in organic compounds
STD 11 (Chemistry) - Hybridization in organic compounds
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Molecular Orbital Theory II: MO
Molecular Orbital Theory II: MO's of the H2 Molecule
Published: 2011/08/06
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Valence Bond Theory ( Animation ) : Dr. Amal K Kumar
Valence Bond Theory ( Animation ) : Dr. Amal K Kumar
Published: 2013/10/30
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Valence Bond Theory - Part 3 | Chemistry Animation Video | Hybridization Lecture and Hybridization
Valence Bond Theory - Part 3 | Chemistry Animation Video | Hybridization Lecture and Hybridization
Published: 2012/12/10
Channel: ClassteacherCTLS
HYBRIDIZATION | شرح التهجين فى المركبات العضوية
HYBRIDIZATION | شرح التهجين فى المركبات العضوية
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Published: 2014/04/08
Channel: 7activestudio
section 7 5 sigma and pi bonds 2
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Published: 2012/03/05
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10- Covalent bond by Orbital Molecular Theory for Carbon Monoxide
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Published: 2014/05/28
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Sigma and Pi Bonds: Hybridization Explained!
Sigma and Pi Bonds: Hybridization Explained!
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Channel: chemistNATE
Boding Vs Anti bonding Molecular Orbital - Differences of Boding and Anti bonding Molecular Orbital
Boding Vs Anti bonding Molecular Orbital - Differences of Boding and Anti bonding Molecular Orbital
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Ionic and covalent bonding animation
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Published: 2013/04/09
Channel: AK LECTURES
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Sigma & pi-bonds in Fluorine,Nitrogen & Oxygen - Dr.Amal K Kumar
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Published: 2012/12/05
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Hybridization Theory (Preview)
Hybridization Theory (Preview)
Published: 2009/04/11
Channel: SponholtzProductions
How To Find Hybridization | Easiest Method | Trick to Find Hybridization | XI-XII | IIT JEE (Hindi)
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Published: 2017/06/26
Channel: Daniel Rizvi
Co-ordinate Covalent Bond
Co-ordinate Covalent Bond
Published: 2011/12/29
Channel: 7activestudio
sigma and pi bonds
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Published: 2008/05/30
Channel: Janet Coonce
SP2 Hybridization
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Published: 2011/11/28
Channel: 7activestudio
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Orbital structure of Benzene
Published: 2015/05/27
Channel: MBD Alchemie
Valence Bond Theory for Dioxide Carbon orbitals-sp
Valence Bond Theory for Dioxide Carbon orbitals-sp
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Tricks of Molecular Orbital Theory, Part-I (IITJEE Mains/Advance/AIIMS/NEET/XI/XII)
Published: 2016/06/05
Channel: Er Dushyant Kumar-B.tech,IIT Roorkee
Understanding Overlapping Atomic Orbitals
Understanding Overlapping Atomic Orbitals
Published: 2015/03/18
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Covalent Bonding
Covalent Bonding
Published: 2015/11/04
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Molecular Orbital Theory Organic Chemistry Introduction
Molecular Orbital Theory Organic Chemistry Introduction
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Valence Bond Theory
Valence Bond Theory
Published: 2014/01/31
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Formation of Molecular Orbitals
Formation of Molecular Orbitals
Published: 2015/10/28
Channel: CBSE
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
  (Redirected from Natural Bond Orbital)
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In quantum chemistry, a natural bond orbital or NBO is a calculated bonding orbital with maximum electron density. The NBOs are one of a sequence of natural localized orbital sets that include "natural atomic orbitals" (NAO), "natural hybrid orbitals" (NHO), "natural bonding orbitals" (NBO) and "natural (semi-)localized molecular orbitals" (NLMO). These natural localized sets are intermediate between basis atomic orbitals (AO) and molecular orbitals (MO):

Atomic orbital → NAO → NHO → NBO → NLMO → Molecular orbital

Natural (localized) orbitals are used in computational chemistry to calculate the distribution of electron density in atoms and in bonds between atoms. They have the "maximum-occupancy character" in localized 1-center and 2-center regions of the molecule. Natural bond orbitals (NBOs) include the highest possible percentage of the electron density, ideally close to 2.000, providing the most accurate possible “natural Lewis structure” of ψ. A high percentage of electron density (denoted %-ρL), often found to be >99% for common organic molecules, correspond with an accurate natural Lewis structure.

The concept of natural orbitals was first introduced by Per-Olov Löwdin in 1955, to describe the unique set of orthonormal 1-electron functions that are intrinsic to the N-electron wavefunction.[1]

Theory[edit]

Each bonding NBO σAB (the donor) can be written in terms of two directed valence hybrids (NHOs) hA, hB on atoms A and B, with corresponding polarization coefficients cA, cB:

σAB = cA hΑ + cB hB

The bonds vary smoothly from covalent (cA = cB) to ionic (cA >> cB) limit.

Each valence bonding NBO σ must be paired with a corresponding valence antibonding NBO σ* (the acceptor) to complete the span of the valence space:

σAB* = cA hΑcB hB

The bonding NBOs are of the "Lewis orbital"-type (occupation numbers near 2); antibonding NBOs are of the "non-Lewis orbital"-type (occupation numbers near 0). In an idealized Lewis structure, full Lewis orbitals (two electrons) are complemented by formally empty non-Lewis orbitals. Weak occupancies of the valence antibonds signal irreducible departures from an idealized localized Lewis structure, which means true "delocalization effects".[1]

Lewis structures[edit]

With a computer program that can calculate NBOs, optimal Lewis structures can be found. An optimal Lewis structure can be defined as that one with the maximum amount of electronic charge in Lewis orbitals (Lewis charge). A low amount of electronic charge in Lewis orbitals indicates strong effects of electron delocalization.

In resonance structures, major and minor contributing structures may exist. For amides, for example, NBO calculations show that the structure with a carbonyl double bond is the dominant Lewis structure. However, in NBO calculations, "covalent-ionic resonance" is not needed due to the inclusion of bond-polarity effects in the resonance structures.[2] This is similar to other modern valence bond theory methods.

See also[edit]

References[edit]

  1. ^ a b Weinhold, Frank; Landis, Clark R. (2001). "Natural Bond Orbitals and Extensions of Localized Bonding Concepts" (PDF). Chemistry Education Research and Practice. 2 (2): 91–104. doi:10.1039/B1RP90011K. 
  2. ^ Weinhold, Frank; Landis, Clark R. (2012). Discovering Chemistry With Natural Bond Orbitals. New Jersey: John Wiley & Sons. pp. 132–133. ISBN 978-1-118-22916-3. 

External links[edit]

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