Subject: CCL. HYBRIDIZATION NOT "REAL";V. FOCK

From: Eric Scerri <[email-masked]>
Date: Mon, 11 Sep 2000 22:34:17 -0800

>Quantum Mechanics is a mathematical methodology which best (at this 
>time) reproduces existing knowledge.  As such it is an approach that 
>we can use to understand our physical universe.  While it describes 
>what we perceive as reality, it is no more "real" than the theory of 
>phlogiston nor are its constructs (i.e orbitals - hybridized or not) 
>any more real than the billiard ball representation of atomic 
>structure.

While I agree with the jist of this statement I wonder whether you 
might be overstating the case?

Phlogiston theory was long ago refuted and is therefore not even 
candidate for a true scientific entity.

Not all the entities discussed by quantum mechanics have the same 
status surely?
Most people would want to say that electrons and protons are real entities.

Your statement could be taken to mean that QM is a theory 
(epistemology) and therefore may not give us direct access to real 
entities (ontology).

But there is a problem that we can only get at the micoworld via 
quantum mechanics so the neat distinction between the world and our 
description of the world is blurred.

I wonder whether you also intended the first sentence literally, 
namely that QM makes no true predictions?  If so I think this is 
debateable although it is probably true that there are few genuine 
predictions, in the temporal sense, made by QM.

To get back to the main issue we can distinguish between atomic 
orbitals (non real) and electron density (real).  Each case can be 
dealt with separately whereas a general statement about quantum 
mechnics as a whole, as above, would suggest that all entities are 
lacking physical reality which to repeat is going too far.

eric scerri

>
>These are all artificial constructs that help us humans find a frame 
>of reference in which we can understand the reality in which we are 
>immersed.  They have no 'reality' beyond that we assign them to 
>enhance our understanding ...
>
Jim Kress

-------------------------------------------------
Dr. Eric Scerri,
Department of Chemistry & Biochemistry,
Charles E. Young Drive,
UCLA,
Los Angeles,  CA 90095
USA

E-mail:   [email-masked]

Editor of "Foundations of Chemistry"
http://www.wkap.nl/journalhome.htm/1386-4238

Also see,
International Society for the Philosophy of Chemistry
http://www.georgetown.edu/earleyj/ISPC.html

---

From: "Oscar N. Ventura" <[email-masked]>
Date: Tue, 12 Sep 2000 08:26:55 -0300 (GRNLNDST)

> lacking physical reality which to repeat is going too far.

It seems to me there's a confussion here. Atomic orbitals (or molecular,
localized, canonical, Kohn-Sham, etc, etc....orbitals) are not less "real"
than total, electron, differential, etc, etc....densities, provided we
could arrive to an agreement of what "real" means. Both orbitals
and densities can be obtained from the same theory and (to a point) 
even offer similar descriptions of the microworld. Physics tells us
however that density is observable, i.e. that we can also construct some
experimental devices which measure this property. So we should be talking
about observability (i.e. the ability of an observer to obtain information
from an object which can be the subject of measurement) and not reality
(which I would not dare to define, but seems to imply the object to exist
independently of any observer and as such it is metaphysics, not physics).

Total density (STM), differential density (X-ray), energies of single
electrons within a molecule (photoelectron spectroscopy) are observable.
Molecular or atomic orbitals, energies of the molecular orbitals, etc, are
constructs of the theory and are not observable.

Just my $ 0.015.

Oscar 

-------------------------------------------------------------------------------
Prof.Dr.Oscar N. Ventura             Tel.+(5982)9248396 Fax +(5982)9241906
MTC-Lab,Facultad de Quimica          MTC-Lab  http://bilbo.edu.uy/MTC-Lab.html 
Universidad de la Republica
Gral.Flores 2124, C. C. 1157         All opinions are my own, and not
Montevideo 11800, URUGUAY            necessarily those of my employer          

"Violence is the last refuge of the incompetent." --- Salvor Hardin 
-------------------------------------------------------------------------------

---

From: "Isaac B. Bersuker" <[email-masked]>
Date: Tue, 12 Sep 2000 09:33:55 -0700

I agree with your statement.

I entered this discussion just to remind people that hybridization may be
obtained from perturbation theory (mixing of s, p, d,... orbitals under the
influence of the field of other atoms, bonding), and hence it is not just an
arbitrary assumption (as it may appear at first sight). It leads to quite
observable charge redistribution (s type admixture in different situations can
be obtained also from spectroscopic data).

This simple remark lead some people to global philosophycal deduction like
"orbitals are not real", "quantum mechanics is not real", etc. I believe that
such statements were of some interest 50 to 60 years ago, not now. It is well
known that our knowledge is relative (not absolute) truth, but as a relative
truth quantum mechanics is excelent with its predictions which are confirmed
by experimental data.

Isaac Bersuker

Eric Scerri wrote:

> time) reproduces existing knowledge. As such it is an approach that we can use
> to understand our physical universe. While it describes what we perceive as
> reality, it is no more "real" than the theory of phlogiston nor are its
> constructs (i.e orbitals - hybridized or not) any more real than the billiard
> ball representation of atomic structure.
>
> While I agree with the jist of this statement I wonder whether you might be
> overstating the case?
>
> Phlogiston theory was long ago refuted and is therefore not even candidate for a true scientific entity.
>
> Not all the entities discussed by quantum mechanics have the same status surely?
> Your statement could be taken to mean that QM is a theory (epistemology) and
> therefore may not give us direct access to real entities (ontology).
>
> But there is a problem that we can only get at the micoworld via quantum
> mechanics so the neat distinction between the world and our description of the
> world is blurred.
>
> I wonder whether you also intended the first sentence literally, namely that
> QM makes no true predictions? If so I think this is debateable although it is
> probably true that there are few genuine predictions, in the temporal sense,
> made by QM.
>
> To get back to the main issue we can distinguish between atomic orbitals
> (non real) and electron density (real). Each case can be dealt with separately
> whereas a general statement about quantum mechnics as a whole, as above, would
> suggest that all entities are lacking physical reality which to repeat is
> going too far.
>
> eric scerri
>
>      These are all artificial constructs
> that help us humans find a frame of reference in which we can understand the
> reality in which we are immersed. They have no 'reality' beyond that we assign
> them to enhance our understanding ...
>
> Jim Kress
>
>

--
Dr. Isaac B. Bersuker
Institute for Theoretical Chemistry
Department of Chemistry & Biochemistry
The University of Texas at Austin
Austin, TX 78712, USA
Ph: (512) 471-4671
Fax: (512) 471-8696
Email: [email-masked]