I know it’s an odd question, but here’s the thing: when I was an elementary/middle schooler in the 1960s/1970s, we had an image of an atom that had a bunch of electrons whizzing about a nucleus - more or less like most of these:
I know that our understanding of quantum physics has expanded greatly since then and that the cute little thingies orbiting the nucleus are more art than reality (it’s my understanding that the distances are far, far, FAR greater than the typical pic suggests).
But - does the iconic image still hold? It doesn’t matter if it is perfectly accurate; of course it isn’t, it never was. But is it the sort of thing that might still appear, without making real physicists cringe, on the cover of a high school physics textbook or in some similar context?
(In case you wonder why I’m asking, I want to decorate a cake to welcome home my son after a summer spent studying quantum mechanics. But I don’t want to create something so, you know, last century.)
The 1960/70s was already about 40 years late to the party for understanding that that diagram is wrong. Schrödinger worked the core basis of his wave equation out in 1925.
If you want to be cute, decorate the cake with a cat.
If you do make a Feynman diagram, make sure you make a valid one. If you don’t understand them, it’d be easy to make something that would look the same to a layman, but which might not even be recognizable to someone who does know them (at best, you’d get “I think that was maybe supposed to be a Feynman diagram, but if so, he messed it up”).
If it’s an electromagnetic diagram, then as long as every vertex has exactly three lines meeting at it, one with an arrow going in, one with an arrow going out, and one with a squiggly line, you should be OK (though you might of course end up with an extremely silly diagram).
Yes, I remember that one. I think which representation of an atom you want to use depends on depends on what you’re trying to study/emphasize.
This one was good enough to tell the rest of the Coast Guard I was an Electronics Technician and not a Bosun’s Mate, Electrician’s Mate, or Storekeeper, etc.
Thanks all - For this case, I think I’ll go with the Feynman diagram, carefully copied for accuracy. (The Schroedinger’s cat jokes are already overused in our household.) It does have the advantage of being extremely easy to reproduce. We’ve also watched several Feynman videos together as a family, so it is fitting.
One again the Dope comes through!
(PS - further physics-related cake decorating ideas still welcome - when he turns 18 in a few months, I’ll need another one.)
Okay, now that that’s taken care of, can we go off on tangents now?
I take a slightly different point of view about all those “incorrect” notions on atoms that have come and gone since atoms were discovered. In my chemistry class, we had a bit of lecture on the history, showing the evolution of those diagrams.
The early chemists and physicists weren’t dumb, and I don’t like to think of there work as “incorrect”. I would suggest “incomplete” instead. J. J. Thomson, for example, no dummy, proposed the “plum pudding” model, which envisioned the atom as an amorphous blob of positive charge with negative electrons floating throughout it. Instead of calling that a “wrong” model of the atom, how about calling it an “incomplete” model – that is, based not on any overtly incorrect knowledge of the atom, but rather on an absence of more detailed knowledge.
Later, when the nucleus and its structure were discovered, the “planetary” model became very popular. That’s the famous image we all grew up with, like the OP was familiar with. Electrons orbited at various specific radii called “shells” and occasionally popped from one shell to another. Now we’re told that even that isn’t right. But again, I think of that as being correct as far as it goes, based on the knowledge of the day, but simply incomplete.
In this interpretation, the more modern view, with electrons shown as probability density clouds, does not replace the old “shell” model, but rather fleshes it out with more complete and more accurate detail. Thus, in true Heisenbergian complementariness, our knowledge of electrons has become increasingly clear as the electrons themselves have become increasingly fuzzy.
Well, I don’t believe the earlier researchers were dumb or lazy or anything, but I don’t think you can really avoid saying that their ideas were just wrong. The positive charge in an atom is concentrated in a tiny tiny central nucleus. It’s not spread out across the atom, period. A model that makes that claim is incorrect, not incomplete – you can’t add anything to it that makes it correct. Thomson didn’t have the experimental evidence that disproves his model, so there’s no blame to him, but his idea was just wrong.
The planetary model is a bit less clear. It’s still wrong but understanding why requires abandoning a lot of commonsense ideas about how objects have locations and trajectories, and replacing them with incomprehensible quantum mechanical notions. The planetary model is perhaps the closest to “correct” as you can get while still retaining the classical idea of what a scientific model is.
Being a smart kid I knew about molecules & atoms and electrons, protons, neutrons etc. since grade school. Always thru, of course, the old Rutherford model diagram. When I finally took my first high school chemistry class and was presented with the newer 3D models, I was like, “Ahhhh, how long has this been around and why wasn’t I notified?!?”. Nobody else in the class seemed to care…
I’m with Senegoid that I would hesitate to call such models outright “wrong”.
It’s like when people talk of Newtonian physics being wrong, usually as some jumping off point for declaring what scientists think they know today will probably be discarded tomorrow.
However, I’ve heard in some cases such people may be sat inside buildings where the engineers took no account of relativistic physics whatsoever :eek:
Similarly I hesitate to call the planetary model “wrong” while it can still be used to make useful predictions / calculations. It’s a “coarse” model.
Note that there are two “planetary” models discussed here. The Rutherford model which is basically exactly a purely-classical solar system with the nucleus as the sun and the electrons as planets (which is the origin of the iconic “atom” image), and the Rutherford-Bohr model which includes a little bit of quantum mechanics to explain the shells (and the fact that orbiting electrons don’t radiate away all their energy until the atom collapses).
As a kid, I read in my Golden Book of Chemistry Experiments that the iconic image of the atom was wrong. But people continue to use it because, well, it’s iconic. It uniquely represents the situation in a way that a fuzzy spherical cloud of electrons don’t, or that higher atomic orbitals (which can look downright obscene in some cases) don’t.
Nowadays those atoms have a “retro” feel to them. Carrtoonists like Pat Oliphaunt used them scattered around a failed nuclear power plant to indicate leakage. Don’t look for them to go asway.
One of my favorite comments on this is from Alan Moore’s Watchmen – they try to get Dr. Manhattan to wear a helmet with this atomic symbol on it. He refuses. “If I wear a symbol,” he says, “it will be one I respect.” He themn draws that single circle with a dot around a dot as nucleus on his forehead. Using a proper schematic as a symbol for the atom. Gotta love it.
