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ChemWiki: The Dynamic Chemistry E-textbook > Wikitexts > UC Davis > UCD Chem 124A: Kauzlarich > ChemWiki Module Topics > Electronic Orbital Energies

Electronic Orbital Energies

Orbital energy varies based on the nth orbital (ONLY FOR HYDROGEN). As n increases, the level of orbital energy also increases. Based on the level of energy of n, the electrons in an atom can be easily removed, or require more energy to be removed.

Properties that Affect Orbital Energy

Since the size of an orbital is determined by the angular momentum, amount of energy, and magnetic moment, these factors would affect the orbital energy.

  • Amount of energy in an electron is represented by quantum number n. The higher the number n, the greater the radius cloud of the electron orbital.**
  • Quantum number l describes the angular momentum of the electron in the orbital. The greater the number, l, the higher the value of the energy.**
  • Magnetic moment number, represented by m. The magnetic moment number indicates the orbital's orientation in space.**

**Refer to http://chemwiki.ucdavis.edu/Wikitexts/UCD_Chem_124A%3a_Kauzlarich/ChemWiki_Module_Topics/Electronic_Quantum_Numbers for further information related to quantum numbers.

Electronic Orbital Energy Patterns on Periodic Table

 

This is an image of the orbital energy diagram of 1,3 butadiene. From this image, you can see the molecular orbitals, as well as the electron configuration.

http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch10/butadienemo.jpg

Aufbau principle, Pauli Exclusion principle, and Hund's Rule can help you in constructing the Molecular Orbital Diagram. Aufbau's principle states to fill electrons up from the lowest energy orbital to a higher energy orbital. Pauli Exclusion principle states that only two electrons can be filled in a single orbital. Meanwhile, Hund's Rule tells us that only one electron can be filled in orbitals with the same energy level before all individual orbitals in the same energy level are filled with a single electron (usually filled with an up arrow).  

How to Construct an Orbital Energy Diagram

This image represents a molecular orbital diagram for B2. This particular structure is used for all atoms below Oxygen. Drawing F2 on a molecular orbital diagram would require another structure of the orbital diagram. See next image.

http://www.chem.queensu.ca/people/faculty/mombourquette/firstyrchem/molecular/orbitals/boron.gif

 

This image of the molecular orbital diagram describes that of F2. As you can see, the diagram for the 2p orbital differs from that in B2; here, the electrons enter sigma bonding orbital before entering pi bonding orbital. Then it fills up the pi anti bonding orbital before filling in the sigma anti bonding orbital.

http://img.sparknotes.com/figures/8/83ce1fb7be648ede5785ea60c96b495c/general.gif

 The molecular diagram varies between diatomic molecules of H2 through N2 from that of diatomic molecules of O2 through Ne2 comes from the different energies in orbitals. It was calculated that the molecules of O2 through Ne2 have σ 2p orbitals in lower energy than π 2p.

References

  1. Kemnitz, Carl. "A primer for students of Organic Chemistry."  2005
  2. Whitten, Kenneth W. Chemistry. Edition 9. Brooks/Cole, Cengage Learning, 2010. Pages 333-334

Outside Links

  1. Petrucci, Ralph H., William S. Harwood, F. Geoffrey Herring, and Jeffry D. Madura. General Chemistry: Principles and Modern Application. Ninth ed. New Jersey: Pearson Prentice Hall, 2007.
  2. Housecraft, Catherine E. and Alan G. Sharpe. Inorganic Chemistry. Third ed. England: Pearson Prentice Hall, 2008.

Problems

  1. Construct a molecular orbital diagram of O2. Explain why the orbital energy diagram of O2 differs from that of He2.
  2.  How do quantum  numbers affect the orbital energy?

Contributors

  • Name #1 here (if anonymous, you can avoid this) with university affiliation

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Last Modified
10:15, 2 Oct 2013

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