From chemistry-request@server.ccl.net Thu Oct 4 12:27:04 2001 Received: from soul.helsinki.fi ([128.214.3.1]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id f94GR4B28560 for ; Thu, 4 Oct 2001 12:27:04 -0400 Received: from localhost (mpjohans@localhost) by soul.helsinki.fi (8.9.3/8.9.3) with ESMTP id TAA19080; Thu, 4 Oct 2001 19:26:34 +0300 (EET DST) X-Authentication-Warning: soul.helsinki.fi: mpjohans owned process doing -bs Date: Thu, 4 Oct 2001 19:26:33 +0300 (EET DST) From: Mikael Johansson X-Sender: To: Ulrike Salzner cc: ccl Subject: Re: CCL:size of s,p,d orbitals In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hello Ulrike and All! On Thu, 4 Oct 2001, Ulrike Salzner wrote: > until 1 hour ago, I firmly believed that p-orbitals are larger than s- > orbitals for atoms that are in the same row of the periodic table. Only [...] > third year students. She told me that she was surprized that the students > did not know that the order according to decreasing size is s > p > d [...] > The question now is: Do the two ways to determine the size of the orbitals > lead to different conclusions? Is there a mistake somewhere? Is there > newer information? Which orbitals are bigger? What is best method to > determine the size to explain bonding, hybridization, or lack thereof and > so on? This was an interesting question, succeeding in diverting me from things I should be doing :-) Without taking a stand on what method is the "best" I made a quick calculation on the argon-atom and compared the "sizes" of the 2s/2p and 3s/3p orbitals. Below is reported the radius of a spherical boundary around the atom which contains 90% resp. 95% of the electron density of the orbital in question: (the calculation was made on B3LYP/TZVP level, for no specific reason) 90% 95% 2s 0.65 0.74 a.u. 2p 0.63 0.72 3s 2.14 2.44 3p 2.64 3.06 So according to the above the 2s/2p-orbitals are about as big, whereas the 3s is smaller than the 3p. Other comments on the subject would be very welcome! Have a nice day, Mikael Johansson University of Helsinki Department of Chemistry mikael.johansson@helsinki.fi Phone: +358-9-191 50185 FAX : +358-9-191 50169