New Attempt at Atomic Article

It took me over six months, following my article on molecules, to write the sequel, on atoms. These are just two in a series, intended to introduce the structure of matter to novice readers who want to learn what particle physics is about.  Atoms aren’t the main focus; future articles will focus on electrons, on protons and neutrons, on quarks, and on the forces that hold these objects together.  But the essay on atoms might be the hardest of the set to write (at least I hope so).  The long delay reflects the challenges involved, and as my readers’ wise and helpful criticisms of Friday’s first version confirmed, I didn’t meet them on my first try.

So after some thought, I’ve made another attempt. Critique still welcome from anyone who wants to make suggestions.

Aside from the fact that I fell into a couple of pedagogical traps that anyone who’d taught chemistry would have known about, I also struggled to describe atoms briefly, clearly and accurately because their features are determined by quantum mechanics — that weird but fundamental behavior of our world that we don’t encounter in daily life but is essential to the structure of matter. What’s profoundly confusing to the non-expert (and somewhat confusing even for experts) is that electrons are, on the one hand, best described in many circumstances as point-like particles (much smaller than atoms, and smaller even than atomic nuclei) yet around atoms they are in some way spread out in a very non-particle-like fashion. Well, indeed, thinking of elementary objects like electrons as “particles” will get you into trouble; for one thing, they are really “quanta” of quantum fields, and in most circumstances they behave much more like waves. And yet it is essential to explain that one can try to measure their size — essentially by forcing them, through an appropriate experiment, to reveal whether they, like baseballs, rocks and dumplings, have internal structure.

Ok, I can’t even figure out how to write this paragraph clearly. There needs to be a way to explain this issue, one that is both moderately intuitive and based on accurate and clear physical reasoning…

19 responses to “New Attempt at Atomic Article

  1. I find this analogy fairly accurate and found it makes sense to some people (at the ~high school level):
    Take a long trough of water, like pigs drink out of. Throw a pebble into the trough at one end and you know what happens – a nice wave travels down the trough towards the other end and eventually dies out due to friction in the water. This neat little wave is like a particle – well defined in space and time. The wavelength of this “particle” is maybe a few inches – meaning the water is flat, then within a distance of a few inches rises up, then back down again, then is flat again.
    Now take a much shorter trough, just a few inches long, about the same as the wavelength of our wave/particle, and again throw a pebble in one end. At first a wave travels down the trough again, but then the front of the wave hits the other end of the trough and bounces back just as the back of the wave is getting formed. Pretty quickly you just have a short tough of water sloshing around! You can’t say where you expect the water to be high or low or flat at any given place or time. This is like the electron in an atom – it is spread all over the area within the atom.
    (You can go on to use this setup to discuss quantum uncertainty – the fact that if you stick your hand down at some particular time, you’ll be able to find the water is high at some particular point, but now you’ve also affected the wave in some unknown way, so if you go in to measure the wave again later you still have no idea where to expect it to be high next time.
    And you can discuss quantization, that if the wavelength matches the length of the trough in a nice integer multiple, the front of the wave bouncing off the end of the trough will match up perfectly with the back of the wave getting going, and the result is a very organized sloshing pattern that is constant in time, with a steady amplitude of oscillation for each point in the trough.)

  2. From what I understand, the whole issue is not so much measuring size as it is measuring behavior. The experiments to probe the electron’s size restrict it, pin it down so that it can be poked to see if we find anything inside. The whole concept of size, as if things has a discrete solid surface (As if quanta were little hard balls of stuff.) is misleading, much like the layman’s ideas on matter and energy. A brief article clarifying size, much like your informative article on mass and energy may be appropriate.

    I don’t think you’ll be able to beat the ‘electron is spread around the atom’ idea though, it’s reasonably intuitive and has worked well for many decades, as long as you don’t probe too deeply into just *what* it is spread out that we label ‘the electron’.

  3. This version of the article is balanced and to the point (we are talking about the main physical properties that explain how the constituent particles determine the behaviour of atoms, mainly chemistry).

    Regarding how the atomic number affects the chemistry of a give type of atom, well, the main chemical behaviour of a kind of atom is determined by the number of valence eletrons the atom has, and atomic number affects that basic basic behaviour in to ways: it affects the electronegativity of the valence electrons, and an atom with a larger atomic number will have the valence electrons further away from the nucleus, and that affects those electrons in terms of energy and in terms of a less stronger influence of the positive charges of the protons (they are further away from the valence electrons).

  4. The fact that the chemical behaviour of an atom is determined mainly by the number of valence electrons (the electrons in the outermost layer) is the basis behind the Periodic Table of Elements and The Periodic Law of Elements.

    The Periodic Law and The Periodic Table of Elements was proposed and studied by a russian chemist, Dmitri Mendeleev.

    In many ways, Mendeleev was a precursor of quantum mechanics. Based on the Periodic Table of Elements that he devised, he was able to predict the existence, chemical behaviour and physical properties (like boiling point, density, etc.) of certain elements that were not discovered yet by the end of the XIX century.

    Kind regards, GEN

  5. Albert Einstein conceptually jumped from the byzantine, but effective, Planck Constant assisted computation of Planck on the blackbody radiation. Einstein claimed that the effect hypothesized by Planck was the result not of the status of the emissary body, but of light itself. Einstein claimed that there was such a thing as quanta of light, packets transmitting energy proportional to the frequency of the electro-magnetic wave (1905).
    The Einstein relationship between frequency and energy was confirmed nine years later (Millikan), proving Einstein “Lichtquanten” right enough to get the Nobel for it (1921).

    In 1924, Louis De Broglie generalized Einstein’s photon work, by claiming that all and any process was a wave. So they are not localized, and they interfere, especially with themselves. Energy-momentum is transmitted discreetly though, and depends upon the frequency of the wave. As everything is waves, in process, no fundamental process can be precisely localized (uncertainty principles on position-momentum and time-energy).

    De Broglie’s idea was proven right when two American physicists observed (by happenstance) electronic waves (1927).

    Around an atom an electronic process, that is, a wave, when stable, that is, not transmitting or receiving energy-momentum, has to interfere constructively with itself. Hence the discrete energy levels, corresponding to the frequencies where the positive interference occurs.

    The easiest hypothesis is to make the waves differentiable (so they penetrate materials, except when given a good reason not to). This, plus supplementary hypotheses (the waves represent a probability of existence (standard Copenhagen interpretation), or a “double solution” (De Broglie)) directly predict effects such as the Tunnel Effect (impossible in classical mechanics).

    By guessing what the wave could be one gets the (de Broglie-) “Schrodinger” equation, or the Klein-Gordon. Dirac guessed what the simplest relativistic equation for an electron could be. That brought him to a first order differential equation, and he invented a wave in which it would wave, spin space. Working through the puttive consequences of this equation he found the positron, and QED.

    There will be some day much more to say. How one goes from the wavy process to the localized energy-momentum, the theory does not say, and is therefore incomplete.

    • While your history seems pretty good up through 1930, your last line “there will some day be much more to say” is more than a little astounding to me.

      Dirac’s relativistic equation — relativistic quantum mechanics — was inconsistent. It does not make sense to have quantum mechanics, relativity, and nothing else. And fixing the problems led to relativistic quantum field theory, which has been the story from the 1930s to the present. During that time all sorts of additional conceptual advances have been made. For some reason people seem to think quantum theory stopped in 1930.

      So I would amend your statement: “There is already much, much more to say”. Everything you’ve discussed in this comment is based on quantum mechanics, and it all gets a fresh coat of paint, of a different color, in quantum field theory.

  6. /Einstein claimed that there was such a thing as quanta of light(bundles of energy), packets transmitting energy proportional to the frequency of the electro-magnetic wave (1905).
    Energy-momentum is transmitted discreetly though, and depends upon the frequency of the wave.
    Hence the discrete energy levels, corresponding to the frequencies where the positive interference occurs./

    A wild guess(I stop with this):
    If the nucleus also in quantum state, the weak force interaction(decay) also, has to interfere itself and with electron atmosphere.
    The electron mass is the intensity(high) of those frequencies(we call it soaking with Higgs(h) vev- because other gold stone Higgs eaten by weak forces). The only wanderer is Higgs(h).

    The density of the nucleus may be the intensity of those frequencies(embedded energy bundles). At the point of occupying lower energy level, may be the fulcrum of this density – may be rendered by the lower energy level of many Higgs particles(if anything found).
    This tether the atom with spacetime metric(occupying its position in spacetime curvature).

    Atoms without Higgs(h) is like hydrogen filled balloon. Atoms with Higgs(h) is like atmosphere gas filled balloon.????

    • Nope. Wrong guess. [We do understand this stuff pretty well; after all our equations for these things do a great job of predicting what happens in a wide variety of experiments.]

      • Thank you for your kind answer Professor,
        This Nope occurred from my question in 7th standard(by fuzzy and obscure natural language). I repeatedly asked my science teacher, “why my image in the mirror is not me?”. He was annoyed and said, “it reflect your right into left and left into right, so it is not you”.
        I was unsatisfied, if “reflect” not me, if it return it is me?.

        Why mc^2 ?

        “c” is the speed of the light, not speed of the photons. At speed c we didnt know at what form(phase transition) photon exists, thanks it is massless.
        You have said, two photons travel in opposite directions in a closed system, the system acquire photon mass.
        In this situation, we cannot say the photon(s) travel in opposite directions, roaring around or “returning around” in the closed system like atmosphere ?
        At the point of “return” the momentum will be zero and the speed will be doubled(c^2) ?- though light cannot exceed c it must cancel each other(into nothing- Higgs h)- but before it cancel, it acquire a non zero value as c^2. So photon blackholes disappears?

        Higgs(h) is also nothing and transcendental, wherever its non zero value “vev” occurs, it reacts with every charges and frequencies and increase the intensities of frequencies(quanta or bundles of energies). We interpret as various particles as electron, positron, antielectron, antipositron ect..
        If the density of the intensities is more, we interpret as particle with mass(xc^2)?. Remember, there was tiny masses of various types locked in closed system during Big bang.
        But the Higgs(h) have a peculiar behaviour of exceeding the system and interact outside for a while ?

        I apologise, as I take it for granted quantum state’s non intuitive skips, non classical analogies and anomalies.

        • Just as a side note, a mirror, being a 2D surface reverses two directions in your reflection; left-right and front-back (Something that is further behind you appears further in front of you when seen in the mirror.)

          • Thank you Mr Kudzu, teaching correct science is a service to society.

            Tribal societies(where religions survive) need Enlightenment- eventhough it was told contrary in bible as Adam’s apple(forbidden fruit).
            We did enjoyed the fruits of Enlightenment of last centuries.

            If the wave nature(frequency) and its energy(quanta) is exactly replicated then we have teleportation – is an old science fiction.

            “Nothing to being”, a quantum state of “zero” rhythm, in phase with various frequencies is a “cosmic dance” in micro level(quanta of light proportional to frequency of the electromagnetic wave).
            Where these frequencies intensify, where its phase transition become almost nothing is the question( we interpret that as neutrino oscillation and gauge invariance ).

            We may never going to understand that otherwise for good or bad, some unexpected discoveries may happen like anti gravity vehicles??

            I have to learn more equations Mr Kudzu.

  7. There may be a way to write your paragraph clearly, but I am reminded that even translations from language to language, say German to English, often fall short of conveying the true meaning of certain words and concepts. Even as math may describe phenomena, it is not the phenomena and describing the math with prose draws us even further from the phenomena, a translation of a translation. Maybe it has to be metaphorical or poetic or a series of hums and clicks or some other, as yet, unknown method. Tough one for sure.

  8. Natural languages have their pros and cons.

    Many anthropologists believe that langauge was an evolutionary treat that arose as a tool to solve a major crisis in the chances of survival of our ancestors:

    As our ancestors were competing to survive with other hominids, and those hominids were just as capable as our ancestors to learn by watching, even though our ancestors were smarter and would invent a novel way to survive, it was easy for their competitors to copy that by watching while our ancestors were teaching the young members of their tribe.

    So, our ancestors evolved in a way that their competitors could not replicate: teaching the young with words.

    So, there was value in natural languages to be fuzzy and obscure.

    The advent of so many languages was a natural extension of the same concept: to keep the knowledge within a certain tribe, tribes would have an evolutionary pressure to develop new languages that would change quickly over time.

    Natural languages are not good to gather and document product requirements and product specs, just as they are not any good to do science, and that is for the same reasons that they were good to solve the crisis that gave rise to them.

    Kind regards, GEN

    • I am curious, do you have any references viz ‘to keep the knowledge within a certain tribe, tribes would have an evolutionary pressure to develop new languages that would change quickly over time.’? I myself cannot see how such pressure would arise or how it could be differentiated from the natural drift of language over time. And would there be any pressure to make languages simple and logical? Evolution tends to streamline something important once it has emerged, why do not languages evolve to less costly to learn and understand? A perfect language where you could always be sure of a speaker’s message would surely be a great advantage over the ambiguity we are faced with today.

  9. Dear Matt: Thank you for your kind answer. Sorry I took so long to react. I am also sorry that my sibylline conclusion led you to feel that I believed there has been no progress since Dirac. I was thinking of the duality wave-particle. There was, of course, gigantic progress in Quantum Field Theory. I am a fervent admirer of many of the great ideas of QFT.

    However, QFT is focused towards high energies. As you yourself seem to point out, something is still amiss:
    “[What's] somewhat confusing even for experts) is that electrons are, on the one hand, best described in many circumstances as point-like particles (much smaller than atoms, and smaller even than atomic nuclei) yet around atoms they are in some way spread out in a very non-particle-like fashion. Well, indeed, thinking of elementary objects like electrons as “particles” will get you into trouble; for one thing, they are really “quanta” of quantum fields, and in most circumstances they behave much more like waves… And yet it is essential…to reveal whether they, like baseballs, rocks and dumplings, have internal structure.
    Ok, I can’t even figure out how to write this paragraph clearly. There needs to be a way to explain this issue, one that is both moderately intuitive and based on accurate and clear physical reasoning…”

    Are you suggesting that this “internal structure” is provided by Quantum Field Theory? Is that “fresh coat of paint” enough to settle once and for all the relationship between the wavy aspect and the particle aspect of field quanta? Or, for that matter, any piece of matter whatsoever? Does QFT helps in understanding, say, Quantum Entanglement, and did it help in the new methods elaborated by Wineland and Haroche?

    • new theories try to offer better predictions to a wider set of experiments, with the least amount of parameters and assumptions.

      Theories can’t attempt to settle down issues for many reasons, but one of these reasons is the fact that we do not know have perfect instruments to capture all the details behind a certain physical fenomenum, so, we have no way to verify if certain important aspects are left out of our model to be able to resolve a certain scientific issue once and for all.

      We do have an iterative and incremental approach to a certain aspect of nature, so, over time, we have a broader and deeper understanding of a larger subset of important dimensions and variable that are significant to a certain domain of nature, but that is as far as we can expect to get.

      To understand how science operates, there are certain ideas and concepts pertaining to the scientific method that must be understood and accepted.

      Kind regards, GEN

    • Patrice — thanks for your reply.

      No, I wasn’t saying that Quantum Field Theory (QFT) says anything about internal structure of electrons; quite the contrary. Electrons are pointlike in the current Standard Model. But what QFT does do, compared to quantum mechanics, is change the relationship between electrons, the wave function describing the state of one or more electrons, and the wave-like properties of those electrons.

      By chance, I had a conversation yesterday at the Institute for Advanced Study with several famous theorists about the question of what QFT says about quantum entanglement. No one was aware of any fully relativistic quantum-field-theory treatment of the quantum entanglement arising in, say, the Bell inequality. I assume the same is true for Wineland and Haroche. And this is a serious issue if one wants to draw correct conclusions about locality and causality; it seems unlikely that quantum mechanics alone would allow these subtleties to be properly addressed. So it would appear that there is more research to be done, though it is possible that it has been done and that the people I spoke to are simply unaware of it.

  10. Dear GEN: As Richard Feynman pointed out, the way key insights in science have been brought forward varies so much that there is no such as thing as “understanding how discovering new science operates”… Besides of course, the fact that science, in full, means that experiments, repeated ad nauseam, give always the results that the theory expects. Basically the scientific method is common sense supported by unimpeachable experimental evidence. Operating this method, in turn, leads to a body of knowledge, science itself. New minds have to learn both the method, and the fruits of its application. Indeed.
    Kind regards to you too.

  11. You actually make it seem so easy with your presentation but I find this matter to be actually something that I think I would never understand.

    It seems too complicated and very broad for me.
    I am looking forward for your next post, I’ll try
    to get the hang of it!

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