MadSci Network: Chemistry

Re: Do phosphorus and sulfur have d orbital electrons?

Date: Mon Apr 23 15:03:01 2001
Posted By: Dan Berger, Faculty Chemistry/Science, Bluffton College
Area of science: Chemistry
ID: 987729184.Ch

Do phosphorus and sulfur have d orbital electrons?

The teachers manual for Addison-Wesley's Chemistry on page 428 states that P and S have d orbital electrons. Also, it says that NO3-,OH-, and SO3 are diamagnetic while H20 is paramagnetic.

Would not NO3- have a single unpaired electron? Would not OH- also have just one unpaired electron? I can see that SO3 would not have a single unpaired electron. I would agree that H20 does not have a single unpaired electron.

DISCLAIMER: I have not seen the reported items in the Addison-Wesley teachers' manual for Chemistry. My answer addresses the accuracy of the statements quoted above, and does not necessarily disparage Addison-Wesley's textbook, which I have not seen.

Most of the statements above are either false or misleading.
  • In the ground state, phosphorus and sulfur do not have occupied d atomic orbitals. However, d-orbital hybridization is often invoked to explain the fact that these elements can form more than the usual number of bonds, such as PF5 or H2SO4.

    d-Orbital hybridization is an inadequate model of bonding in such molecules. See this MadSci answer, as well as L. Suidan, J.K. Badenhoop, E.D. Glendening, and F. Weinhold, "Common Textbook and Teaching Misrepresentations of Lewis Structures," Journal of Chemical Education, 72, 583 (1995). Thank you to Eric Scerri for the second reference.

  • Water is not paramagnetic; it is diamagnetic. In fact all of the molecules and ions cited above (nitrate, hydroxide, sulfur trioxide, water) are diamagnetic.

  • If you draw correct Lewis structures for the cited molecules and ions, you will find that all electrons are paired. This is supported by quantum mechanical calculations. But nitrogen trioxide (or hydroxyl radical) should be paramagnetic, because it has a single unpaired electron.

Dan Berger
Bluffton College

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