From chemistry-request;at;ccl.net Thu Jan 20 08:18:19 2005 Received: from smtp2.ruc.dk (smtp2.ruc.dk [130.225.220.22]) by server.ccl.net (8.12.8/8.12.8) with ESMTP id j0KDIIi3014616 for ; Thu, 20 Jan 2005 08:18:18 -0500 Received: by smtp2.ruc.dk (Postfix, from userid 1005) id E09CD238008; Thu, 20 Jan 2005 12:15:58 +0100 (CET) Received: from virgil.ruc.dk (virgil.ruc.dk [130.225.220.110]) by smtp2.ruc.dk (Postfix) with ESMTP id 69419238020 for ; Thu, 20 Jan 2005 12:15:55 +0100 (CET) Received: from VIRGIL/SpoolDir by virgil.ruc.dk (Mercury 1.47); 20 Jan 05 12:15:55 +0100 Received: from SpoolDir by VIRGIL (Mercury 1.47); 20 Jan 05 12:15:48 +0100 From: "Jens Spanget-Larsen" Organization: Roskilde Universitetscenter To: chemistry=at=ccl.net Date: Thu, 20 Jan 2005 12:15:20 +0100 Subject: CCL:orbitals and reality Reply-To: spanget=at=ruc.dk Message-ID: <41EFA0DD.19043.4DBFF8F # - at - # localhost> Priority: normal In-reply-to: <20050119161402.14116.qmail=at=web30803.mail.mud.yahoo.com> References: <41EE2DEC.9030100=at=uibk.ac.at> X-mailer: Pegasus Mail for Windows (v4.01) X-Spam-Checker-Version: SpamAssassin 2.61 (1.212.2.1-2003-12-09-exp) on servernd.ccl.net X-Spam-Status: No, hits=0.2 required=7.5 tests=BAD_X_HEADERS autolearn=no version=2.61 X-Spam-Level: Dear CCL-community! I became curious whether the disagreement in the current discussion on 'Orbitals and Reality' might originate in misleading or unclear presentations in introductory chemistry textbooks. Is the confusion introduced here, leading perhaps to the use of improper language in scientific articles, even by frontline researchers in leading journals? First I looked up Zumdahl's "Chemical Principles" and found the following careful explanation of the situation. Can it be stated more clearly? Yours, Jens >--< Steven S. Zumdahl: "Chemical Principles", Fourth Edition, Houghton Mifflin, Boston 2004. pp673-675: "14.6 Orbitals: Human Inventions "In the treatment of the bonding and structure in molecules we have stressed that the descriptions we have given are models - and simple ones, at that. These models are extraordinarily valuable because they provide pictures in our minds of what molecules might look like and how they might behave. This helps us decide what questions to ask (what experiments to do) as we try to understand more completely the complicated behavior of matter. However, as valuable these pictures are, we must remember that they greatly oversimplify a very complex situation. We must realize that these models can give us a rather superficial view that is often highly misleading. "For example, after all of the talk about orbitals in the last several chapters, you probably have the distinct impression that orbitals actually exist. The truth is, they do not - at least not in the physical sense. Orbitals are mathematical functions - solutions to a modified Schrvdinger equation (the changes made to allow separation into independent electron equations). "Thus orbitals are mathematical tools we use to describe atoms and molecules. However, they have no physical reality in the sense that if you could look at the water molecule you would probably not "see" anything like the pictures we have shown in this book. These pictures merely help us visualize the theoretical imformation we have accumulated for water. (...) "The point made here is ... to make sure that you appreciate the nature of models and that you recognize the difference between the information learned about matter from experiments and the information learned from theories. Because matter is so complex, we often tailor our theories to explain a limited area of nature so as to keep the theories simple enough to understand and use. However, it is very dangerous to assume that such a limited theory can then be used in a wider sense. We must be very careful to ask proper questions of our theories or we face the danger of being greatly misled." =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= JENS SPANGET-LARSEN Office: +45 4674 2710 Department of Chemistry Fax: +45 4674 3011 Roskilde University (RUC) Mobile: +45 2320 6246 P.O.Box 260 E-Mail: spanget=at=ruc.dk DK-4000 Roskilde, Denmark http://virgil.ruc.dk/~spanget =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=