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A Brief Introduction to Molecular Orbital Theory
A Brief Introduction to Molecular Orbital Theory
Published: 2013/04/16
Channel: ChemSurvival
Sigma and Pi bonds
Sigma and Pi bonds
Published: 2014/05/06
Channel: 7activestudio
Valence Bond Theory ( Animation ) : Dr. Amal K Kumar
Valence Bond Theory ( Animation ) : Dr. Amal K Kumar
Published: 2013/10/30
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Orbitals: Crash Course Chemistry #25
Orbitals: Crash Course Chemistry #25
Published: 2013/08/05
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Orbital Molecular Theory
Orbital Molecular Theory
Published: 2009/10/13
Channel: Manuel Moreira Baptista
Electron Orbitals - s,p & d
Electron Orbitals - s,p & d
Published: 2009/11/22
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STD 11 (Chemistry) - Hybridization in organic compounds
STD 11 (Chemistry) - Hybridization in organic compounds
Published: 2015/09/14
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Balloons, Hybrid Orbitals and Multiple Bonds
Balloons, Hybrid Orbitals and Multiple Bonds
Published: 2012/12/18
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Sigma & pi-bonds in Fluorine,Nitrogen & Oxygen - Dr.Amal K Kumar
Sigma & pi-bonds in Fluorine,Nitrogen & Oxygen - Dr.Amal K Kumar
Published: 2013/07/25
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Molecular Orbital Theory Chemistry
Molecular Orbital Theory Chemistry
Published: 2014/01/29
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s and p orbitals, orbitais s e p
s and p orbitals, orbitais s e p
Published: 2009/10/13
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chemistry: shape of orbitals (Techclass Animation)
chemistry: shape of orbitals (Techclass Animation)
Published: 2017/07/15
Channel: Amirtha Institute
3D orbitals animation
3D orbitals animation
Published: 2013/12/15
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SP3 HYBRIDIZATION_ PART 01
SP3 HYBRIDIZATION_ PART 01
Published: 2014/06/06
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Sp,Sp2 Hybridization
Sp,Sp2 Hybridization
Published: 2014/05/28
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H2 Bonding Orbital
H2 Bonding Orbital
Published: 2013/04/07
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Valence Bond Theory, Hybrid Orbitals, and Molecular Orbital Theory
Valence Bond Theory, Hybrid Orbitals, and Molecular Orbital Theory
Published: 2016/01/10
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Pi bond   (π bond) - Simply defined in 30 seconds
Pi bond (π bond) - Simply defined in 30 seconds
Published: 2014/03/14
Channel: Biotech Review
Molecular Orbital Theory
Molecular Orbital Theory
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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
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section 7 5 sigma and pi bonds 2
section 7 5 sigma and pi bonds 2
Published: 2012/03/05
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Hybridization Theory (Preview)
Hybridization Theory (Preview)
Published: 2009/04/11
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Hybridisation / Hybridization (sp, sp2, sp3) Chemical Bonding beryllium chloride benzene methane
Hybridisation / Hybridization (sp, sp2, sp3) Chemical Bonding beryllium chloride benzene methane
Published: 2012/02/04
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Hybrid Orbitals explained - Valence Bond Theory | Crash Chemistry Academy
Hybrid Orbitals explained - Valence Bond Theory | Crash Chemistry Academy
Published: 2017/05/05
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Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Published: 2011/08/01
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Ionic and covalent bonding animation
Ionic and covalent bonding animation
Published: 2008/04/15
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Bonding and Antibonding Molecular Orbitals
Bonding and Antibonding Molecular Orbitals
Published: 2013/04/09
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TYPES OF HYBRIDIZATION PART 01
TYPES OF HYBRIDIZATION PART 01
Published: 2014/04/08
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Hybrid Orbital Formation
Hybrid Orbital Formation
Published: 2008/10/21
Channel: mtchemers
Introduction to the Molecular Orbitals of Conjugated Alkenes
Introduction to the Molecular Orbitals of Conjugated Alkenes
Published: 2013/04/15
Channel: ChemSurvival
Sigma and Pi Bonds: Hybridization Explained!
Sigma and Pi Bonds: Hybridization Explained!
Published: 2012/11/30
Channel: chemistNATE
10- Covalent bond by Orbital Molecular Theory for Carbon Monoxide
10- Covalent bond by Orbital Molecular Theory for Carbon Monoxide
Published: 2012/04/22
Channel: Manuel Moreira Baptista
Resonance in Benzene
Resonance in Benzene
Published: 2010/11/30
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Valence Bond Theory - Part 1 | VBT Animation Video | Hybridization Lecture and Hybridization
Valence Bond Theory - Part 1 | VBT Animation Video | Hybridization Lecture and Hybridization
Published: 2012/12/05
Channel: ClassteacherCTLS
SP2 Hybridization
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Published: 2011/11/28
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Atomic Orbital Hybridization sp3 - Mr. Causey
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Tetrahedral bond angle proof | Structure and bonding | Organic chemistry | Khan Academy
Tetrahedral bond angle proof | Structure and bonding | Organic chemistry | Khan Academy
Published: 2012/09/26
Channel: Khan Academy Organic Chemistry
Co-ordinate Covalent Bond
Co-ordinate Covalent Bond
Published: 2011/12/29
Channel: 7activestudio
Oxygen - Chemistry Cartoon
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Published: 2013/10/22
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The Electron Cloud Model explained + Animation & atomic Orbitals tutorial; Crash Chemistry Academy
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Published: 2015/09/18
Channel: Crash Chemistry Academy
Molecular Orbital Theory Organic Chemistry Introduction
Molecular Orbital Theory Organic Chemistry Introduction
Published: 2014/01/21
Channel: Knowbee
sp3 hybridized orbitals and sigma bonds | Structure and bonding | Organic chemistry | Khan Academy
sp3 hybridized orbitals and sigma bonds | Structure and bonding | Organic chemistry | Khan Academy
Published: 2010/07/23
Channel: Khan Academy
Carbon Hybridization sp3
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Published: 2014/01/26
Channel: Animatedchemistry
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Crystal Field Theory Chemistry Animation Energy Video Lecture on Crystal Field Splitting Theory
Published: 2015/11/10
Channel: Mark Boxer
Formation of Molecular Orbitals
Formation of Molecular Orbitals
Published: 2015/10/28
Channel: CBSE
Understanding Overlapping Atomic Orbitals
Understanding Overlapping Atomic Orbitals
Published: 2015/03/18
Channel: Clutch Prep
Electron Configuration
Electron Configuration
Published: 2013/08/04
Channel: Bozeman Science
Potential Energy vs. Internuclear Distance (Animated) : Dr. Amal K Kumar
Potential Energy vs. Internuclear Distance (Animated) : Dr. Amal K Kumar
Published: 2013/11/09
Channel: Dr.Amal K Kumar
Electronegativity
Electronegativity
Published: 2008/04/14
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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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