School Chemistry without Quantum Physics?

Chemistry as the science of molecules composed of bonded atoms is based on the physics of Quantum Mechanics QM as the science of atoms. For a chemist like Nobel Laureate Roald Hoffman this state of affairs is problematic: "QM delivers numbers, but not stories".  In particular QM does not offer much of understanding of the physics of covalent bonding as a central concept of chemistry, not even for the Hydrogen molecule $H_2$ formed by two Hydrogen atoms $H$. QM delivers total energy as function of the distance between the protons of the $H$ atoms, and identifies a distance of 1.4 atomic units to have minimal energy. QM thus can identify that there is bond, but cannot tell what is the physics of the formation of the bond. In that sense QM acts like a black box which gives numbers but no understanding. 

This poses a serious problem for chemists since what they have to deal with is precisely the physics of chemical bonding. 

A professional chemist may get by with a black box without "stories", but school chemistry without "stories" cannot work, because learning is based on meaning from understanding a story. This means that educators have invented "stories" of chemical bonding which are not supported by physics of QM, which are propagated in chemistry classes. Stories which contain things like "sharing of electrons", "valence bond", "Lewis structure" and "delocalisation", which cannot be traced back to physics of QM. It seems that school chemistry would be the same even if there was nothing like QM. Strange?

RealQM offers an alternative to QM which gives both "numbers" and "stories based on physics" and thus may give additional meaning to school chemistry.  RealQM gives an explanation of the formation of $H_2$ which can be properly understood also by young students, and parents. 

It appears that educators are satisfied with a school chemistry which is not based on quantum chemistry as physics but on old phenomenological ad hoc models without physics which were developed long before QM. So students of chemistry will not have to meet QM and so not even teachers and what for will then a university professor be paid to teach?

One principle of school education is that it is to be a simplified version of university education which is to be be a simplified version of graduate education which should be close to the research front as present highest level of scientific understanding. But school chemistry is not a simplified version of quantum chemistry as the leading theory of chemistry and so appears to violate this principle. The reason is that it is impossible to make sense of a simplified quantum chemistry, because quantum chemistry itself struggles to make sense. 

The problem with pretending quantum mechanics makes sense

 

Sean Carroll, as leading modern physicist and philosopher, today 100 years after Quantum Mechanics QM was born, offers the general public the following information to digest:

• QM is weird,
• because despite the fact that we are celebrating its 100th Anniversary right now,
• we still don't understand it.
• We need guidance from experiments, and so the only way to do that is to build bigger and better experiments. 
• What if I think about this particular system in a completely new way?
• So in my lifetime anyway, I don't think my job is in danger and being put out of work by the computer revolution.

We hear Carroll say that QM is not understood by modern physicists, who anyway pretend that QM makes sense,  which poses a credibility problem. The only way out of is to come to a better understanding by trying some new way of thinking.

After having declared that he does not understand QM, and nobody else, Carroll tell us during a lengthy presentation that QM makes a whole lot of sense as the basis of modern physics and technology. 

RealQM offers a new way of thinking as a form of QM which can be understood, because it has the form of classical continuum mechanics without conceptual mysteries.

This adds perspective to the review process of a first article on RealQM submitted to Foundations of Chemistry reported in recent posts. 

Wave Functions: StdQM vs RealQM

Let us compare the wave functions of StdQM and RealQM, for simplicity for $H_2$ or $He$ with two electrons, as a preparation to the questions posed in the ongoing review of first RealQM article reported in the previous post. 

The wave function $\Psi (x_1,x_2)$ of StdQM depends on two 3d spatial variables $x_1$ and $x_2$ covering all of 3d Euclidean space $\Re^3$, altogether $\Re^6$. In computation, dimensionally reduced forms are used, for example as a Slater determinant:

•  $\Psi (x_1,x_2)=\psi_1(x_1)\psi_2(x_2)-\psi_1(x_2)\psi_2(x_1)$         (1)

with $\psi_1$ and $\psi_2$ functions over $\Re^3$, as a linear combination of products, which is anti-symmetric in the sense that 

• $\Psi (x_1,x_2)=-\Psi (x_2,x_1)$.

The wave function $\Phi$ of RealQM has the form 

• $\Phi (x) = \phi_1(x)+\phi_2(x)$                       (2)

where $\phi_1$ and $\phi_2$ are functions over $\Re^3$ with common coordinate $x$ with disjoint supports $\Omega_1$ and $\Omega_2$ covering $\Re^3$ with common boundary $\Gamma$, where $\phi_1$ and $\phi_2$ take on the same value.

We see that $\Psi$ has product form (1) and $\Phi$ has sum form (2). We can make a formal connection by

• $\Psi (x_1,x_2)=\phi_1(x_1)+\phi_2(x_2)-(\phi_1(x_2)+\phi_2(x_1)$.    

We understand that the sum form of RealQM makes clear physical sense with non-overlapping supports (addition of charge densities).  To be compared with the product form preferred in StdQM in the presence of overlapping supports, which has unclear physical meaning (products of probabilities). 

A fundamental difference between StdQM and RealQM is the the effective use in computation of one-electron wave functions with overlapping vs non-overlapping supports. This observation can be added to a comparison of StdQM and RealQM coming up in the review process marked in the previous post. RealQM will meet a 100 year investment in StdQM. Watch out for referee reports. 

RealQM vs StdQM under Review

The review process of a first article presenting RealQM to the world of theoretical physics/chemistry, is now under way at the Springer journal Foundations of Chemistry. Five reviewers have been invited and two have accepted so far. 

The review takes place from a background of textbook Standard Quantum Mechanics StdQM from which RealQM will be measured. The consensus is that there is no prediction by StdQM which is in conflict with observation. 

For example, the consensus is that the Heitler-London first StdQM prediction of the binding energy of the Hydrogen molecule $H_2$, which is 35% too small, is not in conflict with observation, because the accuracy of the prediction is very low. The consensus is that improved HL predictions will agree to any given accuracy. 

RealQM for $H_2$ gives on a coarse mesh and energy within 1% deviation, but will meet the high standard of consensus of StdQM of no deviation at all. 

So RealQM will not be able to compete with numbers against high standard of StdQM. But RealQM has an advantage by having linear computational complexity and by offering a clear theoretical explanation of the physics of the covalent bond forming the molecule, because RealQM is based on assumptions of clear physical nature, which is not the case for StdQM. 

It will be interesting to follow the reviewers argumentation expected to be based on the consensus.  

  

An Impossible Task: Quantum Chemistry

Here is a prompt I gave to chatGPT:

• Is it so that chemists have been given the task by physicists to make sense of quantum physics in chemistry, a very difficult if not impossible task?

This is the answer by chatGPT, which is very interesting definitely showing intelligence rarely found in real life. Read and contemplate.

Short answer: yes—historically, chemists were effectively handed that task, and it may well be impossible in the strong sense that was implicitly expected. Let me explain carefully, without rhetoric.

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1. How the Task Was Framed (Mostly by Physicists)

A canonical statement is due to Paul Dirac, who famously wrote (1929) that the fundamental laws needed for chemistry were already known, and that the difficulty was “only” their application.

This framed the division of labor as follows:

• Physicists: discover the fundamental laws (quantum mechanics).

• Chemists: apply them to atoms, molecules, reactions, bonding.

Implicit assumption:

Chemical concepts already exist in quantum mechanics and only need to be extracted.

That assumption is now known to be false.

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2. What Chemists Actually Found

When chemists tried to “apply” quantum mechanics, they discovered something unexpected:

• Quantum mechanics gives wavefunctions and energies.

• Chemistry needs molecules, bonds, structures, reactions.

• These do not appear in the fundamental formalism.

As shown rigorously by Hans Primas and by Robert Woolley, exact quantum mechanics contains:

• no molecular structure,

• no localized bonds,

• no chemically distinguishable molecules.

So the task chemists were given was not “apply the theory,” but rather:

Invent a chemical ontology that quantum mechanics itself does not provide.

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3. Why This Task May Be Impossible (in Principle)

The impossibility is not practical but conceptual.

To succeed fully, chemists would need to:

• derive bond, structure, and molecule uniquely and invariantly

• from the exact quantum formalism

• without arbitrary approximations.

But:

• there is no bond operator,

• no structure observable,

• no unique partition of electrons or space,

• no preferred basis.

All chemically meaningful entities arise only after:

• Born–Oppenheimer separation,

• symmetry breaking,

• orbital localization,

• model-dependent idealizations.

This is why Robin Hendry argues that chemical structure is not derivable but emergent.

So if the original task was:

“Recover chemistry from quantum mechanics”

then yes—it is likely impossible, not just difficult.

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4. Why Chemists Still “Succeeded”

Chemists did succeed—but by changing the task.

Instead of deriving chemistry from physics, they:

• built powerful model frameworks (VB, MO, DFT),

• accepted approximation as constitutive,

• treated bonds and structures as pragmatic theoretical entities.

This made quantum chemistry:

• extraordinarily predictive,

• technologically indispensable,

• but not conceptually foundational.

In effect, chemists became mediators, not applicators:
they made quantum mechanics usable by adding chemistry to it, not extracting chemistry from it.

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5. Was This a Category Error from the Start?

Arguably, yes.

Physics aims to describe:

• universal, invariant, minimal ontology.

Chemistry aims to describe:

• stable, manipulable, explanatory entities at an intermediate scale.

Expecting one to directly ground the other may have been a mistake about how scientific levels relate, not a failure of chemistry.

As Eric Scerri later acknowledged:

dependence does not imply derivability.

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6. So Who Gave Whom an Impossible Job?

Not maliciously, but structurally:

• Physics claimed ontological completeness.

• Chemistry was told to “just apply it.”

• The application required creating concepts the theory does not contain.

That is why quantum chemistry feels permanently provisional:
it is asked to do ontological work with tools that are not ontological.

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7. The Clean Conclusion

Yes—in hindsight, chemists were implicitly asked to do something extraordinarily hard, and possibly impossible:

to recover chemically meaningful entities from a theory that does not contain them.

Chemists responded not by failing, but by quietly redefining success:
from conceptual derivation to predictive control.

The real mistake was not made by chemists,
but by the early belief—common in physics—that

having the fundamental laws automatically gives you the higher-level world.

H₂ showed, at the very first step, that this belief was wrong.

Quantum Chemistry: Success or Failure?

Chemistry as the science of molecules is based on Quantum Mechanics as the science of atoms forming the 250 million known molecules by chemical bonding. In other words, the theoretical/computational foundation of Chemistry is Quantum Chemistry QC, since there is no alternative.  

Let us seek an evaluation of the functionality of QC in this role. We let chatGPT collect some views (references below): 

• Quantum mechanics does not contain chemical structure or bonding in its ontology, so chemistry is not reducible to physics even in principle. (Primas 1981)
• The exact quantum‐mechanical description of matter contains no molecules or structures at all; these appear only through approximations such as the Born–Oppenheimer separation. (Woolley & Sutcliffe 2012) 
• Molecular structure is not part of the ontology of quantum mechanics and emerges only through symmetry breaking and modeling, not derivation from the fundamental theory. (Hendry 2010)
• Although chemistry depends on quantum mechanics, key chemical concepts such as bonding and periodicity cannot be derived from it, so reduction fails conceptually even if physical dependence holds. (Scerri 2007)
• Core chemical concepts like bond and structure do not correspond to entities in quantum mechanics and therefore cannot be reduced to physical descriptions. (van Brakel 2000)
• Chemical phenomena such as reactions and transformations are not definable in physical terms, showing that quantum theory predicts outcomes without providing chemical explanations. (Needham 2008)
• There is no operator or unique quantity in quantum mechanics corresponding to the chemical bond, making the bond a model-dependent construct rather than a fundamental entity. (Shaik & Hiberty 2007)
• The exact quantum‐mechanical treatment of molecules is not only computationally intractable; it is also chemically uninformative. The representations that make quantum mechanics useful in chemistry are not derived by straightforward solution of the Schrödinger equation, but by introducing approximations and conceptual structures that are not part of the fundamental theory. (Woody 2000)
• Quantum chemistry is empirically powerful but fails to conceptually ground molecules, bonds, and structure in its own ontology, so it cannot serve as a foundational explanation of chemistry despite its predictive success. (Summary by chatGPT)

What can we learn from this? That QC is a success as theoretical/computational foundation of Chemistry? Is it possible to twist the above statements indicating failure, into success? After all, QC takes massive super-computer resources. 

In this situation of apparent failure, RealQM offers an alternative foundation with theory directly translated to computer code with linear complexity, see this article submitted to Foundations of Chemistry.

Here is a comment to the post by chatGPT:

• This gets to a real weakness of quantum chemistry: the exact Schrödinger equation does not actually produce molecules, bonds, or reactions in any chemically meaningful way. All the structure chemists care about only appears after imposing strong approximations (Born–Oppenheimer, orbitals, potential surfaces, damping, etc.) that are not part of the fundamental theory. As Andrea Woody and others have argued, the exact quantum description is not just intractable but chemically uninformative. In that sense, quantum chemistry “works” only by departing from the very framework it is supposed to be based on.

Here is what chatGPT delivers when asked to defend against the above views:

• The criticism confuses foundational purity with scientific success. It’s true that the bare Schrödinger equation does not hand us bonds, orbitals, or reaction pathways in closed form—but no physical theory does that for complex systems without modeling, idealization, and coarse-graining. What matters is whether those approximations are physically grounded and empirically reliable. In quantum chemistry they are: from Hartree–Fock and post-HF to DFT and ab initio dynamics, the framework routinely predicts structures, spectra, reaction energies, and mechanisms with quantitative accuracy verified against experiment. That is not a philosophical afterthought—it is the core of how modern chemistry, materials science, and drug design actually work. So quantum chemistry does not “fail”; it succeeds precisely because it shows how rich chemical behavior emerges from quantum laws when treated with disciplined, testable approximations.

Your choice? Note that even in defence mode is it acknowledged that bonds and reaction pathways of prime interest, are not handed. 

I then ask if Philosophy of Chemistry PC can resolve the opposing views of critique and defence and get this response: 

• Philosophy of chemistry does not “fix” the disagreement by choosing a winner, but by showing that the two views use different standards of success. The critics are right that chemistry is not strictly reducible to the bare Schrödinger equation: chemical concepts, structures, and reactions are not derivable without strong approximations and representational choices. But defenders are equally right that quantum chemistry is an extraordinary scientific success, because those approximations are physically motivated, systematically improvable, and empirically validated.

• Philosophy of chemistry resolves the apparent contradiction by reframing it: quantum chemistry fails as a literal, foundational reduction, yet succeeds as an effective, unifying, and predictive theory. What it cannot do—and should not try to do—is eliminate the need for modeling, idealization, and emergence in complex systems. The tension is not a flaw in chemistry, but a feature of how science actually connects fundamental laws to higher-level phenomena.

It seems that the role of PC is to make the devastating critique acceptable into a business as usual. In politics the ruling party can claim complete success even under heavy criticism from the opposition, but the general public has the chance to make a verdict in the next election. 

But in science there is no general public and so the ruling paradigm can resist very strong criticism, until something happens...remember phlogistons...corpuscular theory of light...

References: 

• Primas, H. (1981). Chemistry, Quantum Mechanics and Reductionism. Springer.
• Sutcliffe, B. T., & Woolley, R. G. (2012). “On the quantum theory of molecules.” Journal of Chemical Physics, 137, 22A544.
• Hendry, R. F. (2010). “Molecular structure and the philosophy of chemistry.” In Philosophy of Chemistry (Scerri & McIntyre, eds.).
• Scerri, E. R. (2007). The Periodic Table: Its Story and Its Significance. Oxford University Press.
• van Brakel, J. (2000). The Philosophy of Chemistry. Leuven University Press.
• Needham, P. (2008). “What is the problem with reduction?” Studies in History and Philosophy of Modern Physics, 39(4), 763–776.
• Shaik, S., & Hiberty, P. C. (2007). A Chemist’s Guide to Valence Bond Theory. Wiley.
• Woody, A, (2000). Putting Quantum Mechanics to Work in Chemistry: The Power of Diagrammatic Representation, Philosophy of Science 67.

Why Is Chemical Bonding Still a Mystery?

Chemistry is formed by chemical bonding of atoms into molecules, but the physical nature of a chemical bond appears to be unknown even today 100 years after Quantum Mechanics was formed as the physics of atoms and molecules:

• There is no unique way of defining a chemical bond from quantum mechanics. (Roald Hoffmann)
• The concept of the chemical bond is not a real one; it is a figment of our own imagination. A bond does not exist as an observable entity.( Charles Coulson)
• Quantum mechanics does not provide a definition of a chemical bond. (Richard Bader)
• The exact solution of the Schrödinger equation would not solve the chemical problem. (Per-Olov Löwdin)
• Orbitals, bonds, and structures are models imposed on quantum results, not entities delivered by QM itself. (John C. Slater)
• The chemical bond is not a quantum-mechanical observable. (George C. Pimentel)
• Exact quantum dynamics would still not yield chemical concepts such as mechanisms, bonds, or reaction pathways. (William H. Miller)

The lack of a single convincing theoretical explanation of the physics of chemical bonding, questions the credibility of Chemistry as a science, which is met by (instead of one correct theory) a battery of different explanations including Lewis, VB, MO, CFT, LFT, Band Theory, Quantum Chemistry (HF/DFT), supposed to capture different aspects while partly being contradictory.

But in this rather desperate situation of confusion there may be hope the form of  

• Alternative Computational Foundation of Chemistry 

offering an analysis of covalent chemical bond based on a new form of Schrödinger's equation in physical space with clear physical meaning. If you have ever wondered why one neutral Hydrogen atom $H$ can attract another neutral H to form a $H_2$ molecule as a stable relation, this is for you.

Is is natural to trace the unclear physics of covalent chemical bonding back to the lack of clear physics of Schrödinger's equation in its textbook form. Chemical bonding must rely on clear physics to work, and so cannot be explained by unclear physics. 

Chemistry is real physics and cannot rely on a Schrödinger equation without meaning as real physics. RealQM offers a new Schrödinger equation as real physics, and thus a new foundation of chemistry.

 

Why Philosophy of Physics?

Philosophy of Physics today is largely Philosophy of Quantum Mechanics PQM struggling to give meaning to a QM formed 100 years ago by physicists as modern physics without clear physical meaning. 

PQM then has the double role of (i) cover up lack of meaning and (ii) expose lack of meaning. In either case PQM has a difficult task, which rarely can be pursued at a physics department and so may rather be part of a department of philosophy without physics. Here (ii) invites the critical mind to easy catches, while (i) to be successful requires clever argumentation. 

In both cases the real problem of finding a form of QM with physical meaning is left aside and no progress will take place. The result is that none of the questions about the physical meaning of Schrödinger's equation, formulated in 1926 and still serving as the basis of QM, has been given an answer accepted by the physics community. 

Here RealQM may have something meaningful to offer as a mathematical model of the form of continuum mechanics in physical 3d space with clear ontology. If indeed RealQM does show to function as a physical model of atoms and molecules, then PQM will face a new situation without need to take care of (i)+(ii), and so will have to find a new role, maybe as a challenge to philosophers. 

Leibniz's PII vs RealQM vs StdQM

Leibniz's Principle of the Identity of Indiscernibles PII clashes with the basic idea of identical particles of textbook StdQM: If the electrons of a molecule are identical, that is indiscernible, then they would according to Leibniz be identical and so there would be only one electron present, maybe then in the form of a super-electron distributed over the molecule? 

Leibniz today would object to the idea of identical electrons of StdQM, and so would welcome RealQM where electrons have identity/individuality by occupying separate regions in space with continuity in time. 

Electron individuality has a special role in RealQM with Coulomb repulsion present only between charge densities of different electrons, not within individual charge densities. 

But without individuality, lack of self-repulsion cannot be safely built in, which means that in StdQM self-repulsion has to be actively removed as exchange, which presents a major difficulty.

Recall that the electronic wave-functions of StdQM are required to be anti-symmetric,  that is change sign under swapping of electron labels, while labelling of identical electrons appears as strange as well as sign change without reason. 

Why Philosophy of Chemistry?

This is a comment to the previous post on submission of a RealQM article to Foundations of Chemistry edited by Eric Scerri founder of the 21st century discipline Philosophy of Chemistry. 

What can be the role of a philosophy of chemistry? Why was it formed only recently? To seek answers we ask chatGPT to take on both a defensive and a critical attitude and ask about the role of Quantum Mechanics QM as foundation of chemistry, to get the following condensed answer:

Defense (QM as a strong foundation)

Quantum mechanics is the fundamental theory governing electrons and nuclei, so all chemical phenomena ultimately arise from it. Atoms, bonds, spectra, and periodic trends are, in principle, consequences of quantum laws. Chemical concepts (orbitals, bonds, valence) are higher-level descriptions of underlying quantum reality. Quantum chemistry shows that structures, energies, and reactions can be derived from first principles, even if approximations are needed in practice. Thus, chemistry is autonomous in use but reducible in principle to QM.

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Critique (QM as a limited foundation)

Quantum mechanics constrains what is physically possible, but it does not supply the concepts chemistry depends on. Molecular structure, bonds, functional groups, and mechanisms are not contained in the fundamental equations and must be imposed through approximations and conventions. QM provides calculations, not chemical explanations; multiple quantum descriptions can map onto the same “structure,” showing underdetermination. Quantum chemistry relies on chemical input and interpretation rather than replacing chemical reasoning. Thus, QM is necessary but not sufficient: chemistry remains conceptually and explanatorily autonomous.

 New prompt: Is the role of philosophy of chemistry to handle the contradiction between the two statements?

chatGPT: The philosophy of chemistry addresses the apparent contradiction by clarifying what “based on” means. It distinguishes physical dependence from theoretical reduction and explanatory grounding, showing that chemistry can obey quantum laws without being conceptually derived from them. It analyzes reduction versus emergence, evaluates what counts as explanation, and studies actual scientific practice in quantum chemistry and laboratory work. In doing so, it reframes the conflict: quantum mechanics underwrites chemistry at the physical level, while chemistry retains autonomy in its concepts and explanations.

Summary: We find that a main role of Philosophy of Chemistry is to handle two contradictory views on the functionality of QM as foundation of chemistry. RealQM appears to offer a new foundation with new functionality, where there is no contradiction, and if successful will reduce the need of philosophy to reconcile contradictions.