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ChemWiki: The Dynamic Chemistry E-textbook > Wikitexts > UC Davis > UCD Chem 124A: Kauzlarich > ChemWiki Module Topics > Valence Bond Theory: Multiple Bonding in polyatomic molecules

Valence Bond Theory: Multiple Bonding in polyatomic molecules

When Valence Bond Theory is applied to the multiple bonding in polyatomic molecules, there are two types of bonds that can form: homonuclear and heteronuclear. Homonuclear bonds occur between multiples of the same element and heteronuclear bonds occur between different elements. Homonuclear bonds can occur on a diatomic scale all the way up to large polymers made completely of carbon atoms. However, most polyatomic atoms involve heteronuclear bonds. When considering bonding in polyatomic molecules for VB theory, it is easiest to use a mixture of Lewis structures and Atomic Orbital Hybridization to explain.

Bonding In Molecules

 When trying to figure out the bonding of a molecule, it is a good idea to look at the electronic configuration of the atoms (Housecroft, 120). This allows you to know how many valence electrons you have to work with. Then the number of bonds attached to each atom should be determined using the lewis structure of the molecule. After the lewis structure has been determined, find the hybridization of each atom in the molecule. With the determined hybridization, a picture of the molecule should be easy to create.

Example: Ethyne

Ethyne, or acetylene as it is commonly referred to as, has a lewis structure that shows that there is a triple bond between the two carbon atoms. Using valence orbital hybridization, sp hybridization is determined for triple bonded molecules, which means that carbon has two free 2p orbitals that form 2 pi bonds. Using this info you would draw the two carbon atoms with sp bonds connecting them and the two pi orbitals from each atom bonding with each other. Each hydrogen atom has its s orbital is overlapped with each carbon atom's second sp bond . The molecule overall would have a linear structure.

ethyne.jpg       ethyne 2.jpg

References

  1. Housecroft, Catherine E. and Sharpe, Alan G. Inorganic Chemistry. 3rd Edition. Harlow: Pearson Education, 2008
  2. Petrucci et al. General Chemistry: Principles and Modern Applications. 9th Edition. Upper Saddle River: Pearson Education, 2007

Outside Links

  • This is not meant for references used for constructing the module, but as secondary and unvetted information available at other site
  • Link to outside sources. Wikipedia entries should probably be referenced here.

Problems

1. Provide the lewis structure and hybridization of the carbonyl carbon in formaldehyde.

2. Provide the hybridization of S in SH2 and a picture of the hybrid orbitals.

3. Provide the lewis structure and a drawing of the hybrid orbitals in CHF3.

4. Provide the electronic configuration, hybridization, and lewis structure of PF3.

5. Provide the electronic configuration and a drawing of the hybrid orbitals of CO2.

Answers

1. sp2   formaldehyde.jpg

 

2. sp3   SH2.jpg

3.    chf3.jpg               CHF32.jpg

 

 

4. P=[Ne] 3s2 3p3 ; F=[He] 2s2 2p5 ; sp3    pf3.jpg

 

 

5. C= [He] 2s2 2p2 ; O=[He] 2s2 2p4 ;        co2.jpg

 

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Last Modified
10:17, 2 Oct 2013

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