Do you know a chemical property of a simple atom (molecule) not yet reduced to elementary particule physics?

Question

I am told that chemistry has not been reduced to known elementary particle physics. Usually, we would say that the problem is that the equations are too complex. I am curious to know some simple examples of this difficulty. The simpler is the atom or the molecule in the example the better it is. It would also be interesting to know a property of a complex atom or molecule that we have reduced to elementary particle physics, but it is not what I ask, though it is closely related.

My motivation to ask this question is to get a feeling for how much "evidence" we have that it is only a problem in solving the equations. If we have succeeded for *all* observed properties up to some reasonably high level of complexity (in the number of particles/atoms) and it is seems clear that there is nothing special in the next step except the additional particle/atom, then it is good "evidence" that it is just a problem in solving the equations. Otherwise, maybe there is a more fundamental problem.

RichardL In these modeling, when you say that we must use collected data, do you mean in particular that some (or most) of the parameters in the model are not computed from properties of basic elementary particles, but directly obtained from experimental data instead?

If every parameter is obtained from the basic properties of elementary particles, then it must be a special case. I expect that usually we must rely on data directly collected on the system to evaluate some parameters. I think your example is like that, but I want to clarify this.

Answer 1

It is not just a matter of math which is too complex. Even with the necessary assumptions to reduce the complications involved in the mathematics, even the simplest properties, like phase separation require modeling.

The problems lie in the modeling as well as the mathematics. Molecular orbital calculations for 3 - body (atom) systems are complex enough that perhaps a handful of humans understand the interactions.

Chemical properties are based upon electron interactions. Electrons are not Newtonian bodies, they are probability wave functions dispersed in time and space. They are too small to observe directly. The best a human can do is experiment and make models of their behavior based upon the collected data. I would call this a fundamental problem.

Added:
This is not just a matter of Chemical Properties, but even Physical Properties of monatomic elements. Consider Liquid Helium II (Helium below the lambda point). despite the observable properties of this fluid (now called a Bose fluid or Bose condensate) over the last 60 years, the mathematics to explain these properties is fraught with assumptions and approximations. Just look at the mathematics in the last reference. This is more than a matter of solving the equations.

Humans might refine the model for Bose fluids, but cannot solve these equations without reasonable assumptions. These assumptions lead to solutions which are approximations. And this is for Atomic Helium which might be as simple an atom as you are going to find (it does not form molecules like Hydrogen does).

This is an attempt to explain a set of physical properties (a Bose fluid) for simple atoms (Helium) based upon known elementary particle physics. The mathematics required are indeed complex. Even approximate solutions require approximations based upon conceptual models, which might be wrong.