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CHEM202: Advanced Inorganic Chemistry

Unit 2: Molecular Orbital Theory and Symmetry   Molecular orbital (MO) theory is a detailed explanation of how electrons are distributed in molecules.  In your organic chemistry courses, valence bond theory (VBT) was used to explain chemical bonding and molecular structure.  VBT allows that each atom in a molecule retains its own electrons, located in atomic orbitals.  In this unit, MO theory will be introduced.  MO theory assumes that electrons in a molecule do not belong to single atoms but to the entire molecule as a whole.  It also maintains that electrons are not located in atomic orbitals but molecular orbitals, located in specific spatial regions within the molecule.  These molecular orbitals are used to explain the molecule’s chemical behavior and reactivity.  Knowledge of molecular orbitals is essential to understanding the spectrochemical series and predicting ligand substitution in metal complexes.

Unit 2 Time Advisory
This unit should take you approximately 8.5 hours to complete.

☐    Introduction: 1.0 hour

☐    Subunit 2.1: 1.5 hours

☐    Subunit 2.2: 1.0 hour

☐    Subunit 2.3: 1.5 hours

☐    Subunit 2.4: 2.5 hours

☐    Subunit 2.5: 1.0 hour

Unit2 Learning Outcomes
Upon successful completion of this unit, the student will be able to:

  • Construct simple molecular orbital diagrams, giving consideration to energy levels and electron filling patterns.
  • Define bonding, anti-bonding, and nonbonding orbitals.
  • Determine the bond order of a molecule.

  • Reading: UC Davis: ChemWiki’s “Group Theory and its Application to Chemistry” Link: UC Davis: ChemWiki’s “Group Theory and its Application to Chemistry (HTML)
     
    Instructions: Please read the material covered in section 6.  This material introduces the relationship covered in this unit between molecular orbital theory and symmetry.
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

2.1 Linear Combination of Atomic Orbitals   - Reading: Mark Bishop’s Chemistry Site’s “MO Theory” Link: Mark Bishop’s Chemistry Site’s “MO Theory” (HTML)
 
Instructions: Please read the entire webpage.  This material gives background information on molecular orbitals and bond order.  Please work through the examples presented in the text.
 
Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Web Media: YouTube: Mechanophore’s “Hybrid Atomic Orbitals” Link: YouTube: Mechanophore’s “Hybrid Atomic Orbitals” (YouTube)
     
    Instructions: Please watch the video (runtime = 5:16 minutes).  This material explains the need for hybrid atomic orbitals when discussing chemical bonding.
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Web Media: YouTube: Mechanophore’s “Molecular Orbitals from Hybrid Atomic Orbitals” Link:  YouTube: Mechanophore’s  ”Molecular Orbitals from Hybrid Atomic Orbitals” (YouTube)
     
    Instructions: Please watch the video (runtime = 7:02 minutes).  This material describes how molecular orbitals arise from hybridized atomic orbitals involved in bonding.
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Web Media: YouTube: Mechanophore’s “Linear Combination of Atomic Orbitals” Link:  YouTube: Mechanophore’s “Linear Combination of Atomic Orbitals” (YouTube)
     
    Instructions: Please watch the video (runtime = 4:29 minutes).  This material illustrates what happens during bonding by using a wavefunction approach.
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

2.2 Bonding and Antibonding Orbitals   - Reading: UC Davis: ChemWiki’s “Bonding and Antibonding Orbitals” Link: UC Davis: ChemWiki’s “Bonding and Antibonding Orbitals” (HTML or PDF)
 
Instructions: Please read the entire webpage.  This material gives a brief description of bonding and antibonding orbitals, as well as an example of a homonuclear diatomic molecule, H2.  The outside link at the end of the reading refers to an older version of the molecular orbital theory lecture.  You may watch it here; however, a more recent lecture covering molecular orbital theory is found in subunit 2.4.  
You can access the PDF version of this webpage by clicking “Make PDF” at the top of the page. 
 
Terms of Use: Please respect the terms of use displayed on the webpage above. 

2.3 Symmetry and Overlap   - Reading: UC Davis: ChemWiki’s “Overlap of Atomic Orbitals” Link: UC Davis: ChemWiki’s “Overlap of Atomic Orbitals” (HTML)
 
Instructions: Please read the entire webpage.  Click on the button located at the top of the webpage to activate Java.  The virtual experiment allows you to examine the interactions of overlapping atomic orbitals.  You may rotate the display by clicking and dragging your mouse within the black area.      
  
Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Reading: UC Davis: ChemWiki’s “Sigma Bonding” Link: UC Davis: ChemWiki’s “Sigma Bonding” (HTML)
     
    Instructions: Please read the entire webpage.  Click on the button located at the top of the webpage to activate Java.  The virtual experiment demonstrates a sigma interaction between the two s orbitals. 
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Reading: UC Davis: ChemWiki’s “Symmetry Requirements” Link: UC Davis: ChemWiki’s “Symmetry Requirements” (HTML)
     
    Instructions: Please read the entire webpage.  Click on the button located at the top of the webpage to activate Java.  The virtual experiment demonstrates the interaction between s and p atomic orbitals, resulting in nonbonding molecular orbitals.  An explanation of what occurs is found below the display.    
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

2.4 Molecular Orbital Theory   - Lecture: MIT: Principles of Chemical Science, Fall 2008: “Lecture 14: Molecular Orbital Theory” Link: MIT: Principles of Chemical Science, Fall 2008: “Lecture 14: Molecular Orbital Theory” (Adobe Flash, Mp4, or iTunes)
 
Also available in:
YouTube
 
Instructions: Please watch the lecture (runtime = 51:24 minutes).  Please also watch the first part of Lecture 15 (approx. 3:45) for a conclusion to the lecture on MO theory.
 
Terms of Use: Please respect the terms of use displayed on the webpage above.

  • Reading: UC Davis: ChemWiki’s “Molecular Orbital Theory” Link: UC Davis: ChemWiki’s “Molecular Orbital Theory” (HTML)
     
    Instructions: Please read the entire webpage and work through the five questions found at the end of the reading.  This material ties together all of the material you have learned in Unit 2.     
     
    Terms of Use: Please respect the terms of use displayed on the webpage above.

2.5 Molecular Orbital Diagrams   - Reading: UC Davis: ChemWiki’s “Molecular Orbital Diagrams” Link: UC Davis: ChemWiki’s “Molecular Orbital Diagrams” (HTML)
 
Instructions: Please read the entire webpage.  Click on the button located at the top of the webpage to activate Java.  The virtual experiment allows you to examine what each molecular orbital looks like on the molecule, either individually or together, by examining its isosurfaces.   
 
Terms of Use: Please respect the terms of use displayed on the webpage above.