-3
$\begingroup$

Let us consider the example of Na and Cl. Both atoms are called "neutral" simply because they have the same total number of protons as electrons, yet they have a very weak electric field which is hardly measurable. The electron transfer between two neutral atoms is ultimately driven by the electrostatic force.

Arguments like: This is because atoms and molecules are always trying to achieve the most stable, lowest energy state that they can don't really adress my problem, "lower energy" is not a fundamental force but the outcome of a process caused by electrostatic force.

So, in the end, can we say that this very weak electric field of a neutral atom is the main cause that it can attract electrons of other neutral atoms? Simply because the electrons are not classically like point charges in the same place as the protons?

Is there a more detailed book that deals with this in particular? Because I think this is fundamentally important.

Improve this question
$\endgroup$
11
  • $\begingroup$ While atoms do have zero net charge, the charge distribution is not generally spherically symmetric. And even it originally was for some atoms, like for 2 isolate H atoms, it stops to be, when 2 atoms approach. As the electrostatic potential stops to be spherically symmetric around their nuclei. $\endgroup$
    – Poutnik
    Dec 12, 2022 at 22:47
  • $\begingroup$ somewhat relevant: physics.stackexchange.com/questions/267371/… $\endgroup$
    – Andrew
    Dec 12, 2022 at 23:35
  • 1
    $\begingroup$ @DrMoishePippik what should "quantum force" even mean? Thats not a fundamental force. $\endgroup$
    – Scindus
    Dec 12, 2022 at 23:50
  • 1
    $\begingroup$ @Poutnik so can i really say that it is ultimately initiated by the weak electric field around a neutral atom and the more symmetrical the distribution the weaker this (already weak) electric field becomes? You meantioned it would break symmetrie a bit if 2 atoms approach, but this is somehow circular, because one of the 2 atoms must have been asymmetric by itself from the beginning. $\endgroup$
    – Scindus
    Dec 12, 2022 at 23:54
  • $\begingroup$ It may help if you stop thinking about atoms as natural balls and start thinking there are positive nuclei and probability clouds of negatively charged electrons. $\endgroup$
    – Poutnik
    Dec 13, 2022 at 0:05

1 Answer 1

Reset to default
1
$\begingroup$

You don't need to consider quantum mechanics to arrive at a rudimentary understanding of how two neutral objects containing charges can attract, but it is important nonetheless to understand that quantum mechanical properties are very different from classical ones, as explained for instance in answers in this post. In what follows I start with the classical picture.

Two neutral objects can attract each other because the cancellation of attractive and repulsive contributions from the positive and negative charges is not exact, particularly at close distances, and varies with distance. At long distances the total field of one object becomes very similar to that of a neutral point particle, and is therefore very small and nearly invariant with distance between the objects. Therefore both field and force are negligible. At close distances those contributions don't cancel, in particular because the strength of the field falls with distance. This is why two (real) dipoles can attract (ideal dipoles can only induce mutual alignment). To look into this in more detail you can consult the EM textbook by Griffiths.

What Fritz London et al accomplished was to place these basic ideas from EM on a more solid QM footing by introducing concepts such as the atomic polarizability. This was in part necessary because in the absence of point particles you need a different way of computing the field generated by the electrons.

Improve this answer
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.