What does an atom look like?

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Here’s the standard picture of an atom. Stylish, isn't it? It's elegant, distinctive and memorable. But there's a problem, because this image of ball-like electrons circling a gobstopper-like nucleus in specific, single, elliptical paths is scientifically wrong.

But don't take it from me. Here’s what Richard Feynmann (who won a Nobel Prize for physics for co-developing Quantum Electro-Dynamics) said about such an image in his book ‘Q.E.D. The strange theory of light and matter’ (page 84):

“Shortly after electrons were discovered, it was thought that atoms were like little solar systems, made up of a central, heavy part (called the nucleus) and electrons, which went around in orbits, much like the planets do when they go around the sun. If you think that’s the way atoms are, then you’re back in 1910.”


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The reason that Feynmann is saying, ‘you’re back in 1910’, is because physicists rapidly realised after 1910 that an atom couldn’t consist of electron balls 'orbiting' a ball-like nucleus, because, for one thing, unlike charges attract. The electrons are negatively charged and the protons in the nucleus are positively charged. If an electron was orbiting a nucleus, it would immediately spiral down into the nucleus, giving off light as it went and combine with a proton, destroying the atom's stable state. The physicists concluded that there had to be another way that electrons co-exist with protons in atoms.

As physicists developed their new field of quantum physics, they found several more facts about electrons and protons that were weird, but they did help explain how an atom could be stable. Here's four of them:

1) All particles (electrons, protons, photons etc) can behave as waves. This means that there are no particles in reality in the sense of ball-bearing like objects. All the fundamental particles aren’t particles as you and I might imagine them, but some kind of particle-wave hybrid.

2) It is impossible for anyone to say that electrons circle nuclei. Instead, all we can say is that they occupy a quantum position in close proximity to the nucleus and there are rules as to how many electrons could occupy these quantum positions. The Pauli Exclusion Principle helps specify how this works. As this very helpful science article page points out:

"95% of the time (or any other percentage you choose), the electron will be found within a fairly easily defined region of space quite close to the nucleus. Such a region of space is called an orbital. You can think of an orbital as being the region of space in which the electron lives. Note: If you wanted to be absolutely 100% sure of where the electron is, you would have to draw an orbital the size of the Universe! What is the electron doing in the orbital? We don't know, we can't know, and so we just ignore the problem! All you can say is that if an electron is in a particular orbital it will have a particular definable energy."

3) All fundamental ‘particles’ do not exist tangibly in a specific location. Instead, unless they are ‘observed’, the location of each particle is indeterminate; they can be anywhere and it is only the act of observation that puts them somewhere. The only thing that can be said about their location between observations is the probability of their existence in a certain location.

4) The nucleus of an atom is tiny in comparison to the size of its electron ‘orbits’. It is like a pea sitting on the centre-circle of the pitch in a football stadium.

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With all these new facts under our belt, we can think much more accurately about how an actual, real atom would look. It's more like… er… well… something very odd. To make a stab at depicting an atom, I’ve drawn some illustrations of a hydrogen atom, the simplest of all atoms, with only one electron in ‘orbit’ and one proton in its nucleus. This first illustration takes into account the uncertainty in the location of the electron and the proton. Unfortunately, it’s a really boring image. I can’t imagine anyone wanting to display it and say, ‘that’s an atom’; it’s just a fuzzy blob.

What’s to be done? Interestingly, Richard Feynmann thought of some very clever things about how the atom must work for it to be stable. One key fact he developed was that the nucleus and the electrons in orbit were constantly exchanging photons of light. Electromagnetism, as in magnets and electrical currents etc, is all about charged particles exchanging photons. Feynmann realised that this exchange of photons by charged particles could explain how the atom stayed stable. That’s why the theory he helped develop is called Quantum Electro-Dynamics. (By the way, I do recommend his autobiography ‘Surely you’re joking, Dr Feynmann?’ - it’s lots of fun)

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In this way, in an atom, the electrons aren’t orbiting the nucleus like planets around a sun. Instead, they’re held in position by a constant interplay of photons of light passing between the protons in the nucleus and themselves. My second illustration evokes this idea.

Notice that in this second illustration, there aren’t any blobs or balls depicting electrons or protons. This is because, as mentioned earlier, what we call ‘particles’ aren’t really particles - they're waves too - so drawing them as balls is highly misleading. Fortunately, I can draw photon paths without being a big fibber, although that approach is also a simplification as the photons' paths are subject to uncertainty and interference. In the tiny world of the atom, the photons can even vary in speed and do all sorts of strange things. To be honest, this second illustration is a bit boring too; no one’s going to choose that as a logo any time soon. It looks like a very cheap bicycle wheel.

Fortunately, there is an alternative! There is a beautiful way to portray an atom without putting in ball-bearing electrons, or a fat nucleus, or single orbital paths like some sort of comedy sci-fi cartoon. Here it is:
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Yes, it's a Spirograph image! What’s great about this depiction of the atom is that it elegantly shows the mathematical beauty of an atom, its symmetry and also the dense interplay of photon paths within the atom that keeps its electrons in stable positions around the nucleus. Some people might be unhappy that there's no sign of an electron but keep in mind that an electron is strangely similar to a photon, which we almost always depict as a line of light. For example, Feynmann in his Q.E.D. book (which, by the way, is a demanding but very interesting read) explains that an electron behaves in space-time in a similar way to a photon. On page 91, he states:

"You might be interested to know that the formula for a photon going from place to place in space-time is the same as that for an electron going from place to place if the key number 'n' in the formula is set to zero."


It's also worth mentioning that an electron also has an ability to 'absorb' and 'emit' photons. How does this happen? It would seem to indicate that an electron isn't something distinct from a photon but more like 'a fancy photon with a special power'. Since we know that electrons can behave as waves, and we like depicting wave-like photons as lines, why not depict the electrons as lines? Such an image prevents the false 'physical objects in orbit' image, but avoids having to use the visual non-event of a probabilistic blur.

In conclusion, I hope I've convinced you that if someone shows you the standard, iconic image of an atom, you can say ‘that’s a load of bollocks, atoms are more like Spirographs!’ Such a response won’t be precisely correct, but it is closer to the truth, which is what science is all about.

On a more psychological note, I do think it's worrying that the ‘moons orbiting a planet’ image is still being used as the standard illustration of an atom. It indicates that some people in positions of influence still like to believe what nineteenth century physicists believed about the universe, that it is a big clockwork machine made of tiny, but very tangible little balls that moved around each other. Quantum physics has pointed out that that view is a completely wrong idea; maybe an internet filled with spirograph atoms might banish it, once and for all? It's a fun thought, although I can imagine conversations about such a new image of the atom might be difficult…

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'What's that?'

'Oh, it's an atom.'

'Where are the electrons?'

'They're there.'

'Where?'

'Somewhere. They're some of the lines.'

'They're the lines?'

'Yeah, well, them and the photons, which are particles and straight lines, even though they're curved, but you can't see them, but if you observed them, they'd be different and so I've drawn them as lines, even though they're not, but they're not particles either, so lines it is.'

'Right. Where's the nucleus?'

'It's in the middle.'

'But I can't see it.'

'Yeah.'

'Okay.'

(long pause)

'It does look pretty.'

'Yeah, I thought so too.'


p.s. if you want to make spirograph images on your iPad, Craig Kaplan has made an app and half the proceeds from sales go to the Toronto Sick Kids hospital.

p.p.s. In connection with erroneous descriptions of an atom, I originally began this article by referring to a cover story in the New Scientist magazine in which the writer stated that 'electrons circling an atom's nucleus can only occupy discrete orbitals, each of which accepts only strict number of electrons'. I think it's a bit unfair to single out the New Scientist on this matter, as it is generally excellent with its scientific terminology, and so I've popped the reference here at the end instead. Their letters editor even helpfully contacted me over their depiction and pointed out that an orbital is different from an orbit and can be used in a modern description of an atom. They're absolutely correct and I would make it clear that only the article's statement that electrons circle an atom's nucleus is erroneous. As explained above, it is impossible for us to know what the electrons are doing in their 'orbitals' and saying that they circle the nucleus puts us right back into 1910 territory. We must embrace the spirograph….