Niels Bohr, the Bohr-Rutherford atom and Balmer series, take 2

Niels Bohr, 2nd edition, 11" x 17" linocut print, 2018 by Ele Willoughby

I've just printed a new edition of my portrait of quantum physicist Niels Bohr (1885-1962). One of his most famous contributions to quantum mechanics was the Bohr-Rutherford model of the atom. Bohr is shown next to the Bohr model of the Hydrogen atom (all the concentric circles are actually at the appropriate spacing, proportional to the n squared, which probably reflects on my sanity in some way). Bohr proposed that the orbits of electrons were somewhat like planetary orbits (though circular, and at specific quantized distances). To explain how orbitting charged electrons didn't lose energy and annihilate spectacularly with the so-called "spiral death" (physicists are big on melodrama, I'm telling you), he stipulated that perhaps they simply weren't allowed anywhere but the specific orbits. They could lower their energy state if excited by falling to a lower orbit, giving off a specific photon of a specific colour related to the difference between energy levels. This also explained how the spectra of gases had distinct, thin, spectral lines. I've illustrated this with the Balmer series - because it is composed of lines which are visible to the eye (H-alpha is red and caused by a jump from the 3rd to 2nd orbit; H-beta is cyan and caused by a jump from the 4th to 2nd orbit; H-gamma is indigo and caused by a jump from the 5th to 2nd orbit; and H-delta is violet and caused by a jump from the 6th to 2nd orbit). I've shown both the quantum jumps (squiggly arrows - squiggly lines are tradition for photons) and by the line spectrum below Bohr.

Confession: In the first edition, the model of the atom was behind him. It turns out that if your four year old beloved son/tyrant wakes you in the middle of the night and keeps you up for some time, you probably aren't with it enought to try and print a 6 colour linocut with a tricky registration. I didn't change this print based on an aesthetic decision. I simply messed up the layout but decided to run with it. I decided I like it this way.

A little press for IMPRESSI

I was really gratified to see Art.Science.Gallery share a link to The Austin Chronicle's review of some of the many shows that are part of PrintAustin.

"Next door at Art.Science.Gallery., among a wealth of science-oriented prints, Jenn Schmitt's Periodic Table Printmaking Project draws the most interest. In this collection of 118 prints, 97 artists have used a wide variety of mediums – woodcut, linocut, monotype, etching, lithograph, and more – to depict the periodic table of elements. These tight ranks of small works, filling one wall, are an exhibition in themselves; but don't miss Ele Willoughby's thermochromatic linocuts (in which sections of the ink, when heated, disappear; which makes the Schrödinger's Cat print, in particular, a hoot) and, looming overhead, the life-sized gyotaku print of a full-grown turkey vulture by Adam Cohen and Ben Labay of Inked Animal." - via The Austin Chronicle

Do yourself a favour, and check out the great work being shown, including the full Periodic Table. My little contribution to the Project, is Silicon, below. I think of it as an earth scientist, making up so much of our planet's crust, in quartz, or common in seafloor sediments, including radiolarian skeletons, as well as the crystal form of pure silicon... rather than simply as something which goes into computer chips.

Niels Bohr Block Print

This is a block printed portrait of Danish physicist Niels Bohr (1885-1962), subject of the Mad Scientists of Etsy's November Challenge. Bohr is an obvious choice - the Nobel laureate not only was one of the central figures of 20th century quantum mechanics, godfather of the Copenhagen interpretation, he was known for his generousity, open-mindedness, and clear ethics (which cannot convincingly be said of all of his contemporaries). He advocated sharing knowledge and the peaceful use of nuclear energy. He was also known for taking long walks and thinking out-loud. I often wondered about what Mrs. Bohr thought, faced with his incessant rambling on the interpretation of quantum mechanics.


One of his most famous contributions to quantum mechanics was the Bohr-Rutherford model of the atom. In the print, Bohr is shown in front of the Bohr model of the Hydrogen atom (all the concentric circles are actually at the appropriate spacing, proportional to the n the orbit number squared*). Physicist knew that the atoms were neutral, and yet positive charge was highly localized, in what we now know as the nucleus, from the Rutherford Gold-Foil Experiment. As is traditional in science, this experiment isn't named after those who performed it (Geiger - yes, as in Geiger counter - and Marsden) but after their supervisor, Lord Ernest Rutherford of Nelson. They shot alpha particles (Helium nuclei: 2 protons and 2 neutrons, but all they knew was that they were small and had charge +2) at a very thin sheet of gold foil. Gold can be pounded into sheets which are scarcely a few atoms thick. Anyway, some of the alpha particles bounced right back, which Rutherford famously described thus,

It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. On consideration, I realized that this scattering backward must be the result of a single collision, and when I made calculations I saw that it was impossible to get anything of that order of magnitude unless you took a system in which the greater part of the mass of the atom was concentrated in a minute nucleus. It was then that I had the idea of an atom with a minute massive center, carrying a charge.[2]

So Rutherford proposed his model of the atom by making analogy to the solar system. He postulated that the positive nucleus is like the sun, with negative electrons orbiting like planets. This model seems to have reasonated with the public (and you still see absurb, outdated images to symbolize atomic physics, with a dot and various elipses around it) - but it's wrong. You see, it suffers from ...wait for it... spiral death! Physicists are a melodramatic bunch. You see, accelerating charges, like electrons going in circles, give off light, hence loose energy, so would be expected to spiral into the nucleus and annihilate.


Bohr proposed that the orbits of electrons were somewhat like planetary orbits (though circular, and at specific quantized distances). To explain how orbitting charged electrons didn't lose energy he stipulated that perhaps they simply weren't allowed anywhere but the specific orbits. They could lower their energy state if excited by falling to a lower orbit, giving off a specific photon of a specific colour related to the specific, quantized, difference between energy levels. This also explained how the spectra of gases had distinct, thin, spectral lines. I've illustrated this with the Balmer series - because it is composed of lines which are visible to the eye (H-alpha is red and caused by a jump from the 3rd to 2nd orbit; H-beta is cyan and caused by a jump from the 4th to 2nd orbit; H-gamma is indigo and caused by a jump from the 5th to 2nd orbit; and H-delta is violet and caused by a jump from the 6th to 2nd orbit). I've shown both the quantum jumps (squigelly arrows - squigelly lines are traditional for photons) and by the line spectrum below Bohr.

This is a first edition print (one of eight) on Japanese kozo (mulberry) paper, (12.5" by 17").

*The fact that I needed to make my concentric circles at appropriately spaced radii (and the line spectra are at the right spacing too, of course) probably reflects on my sanity in some way, but you know, how can I resist the Bohr Hydrogen atom? I mean one can actually solve it analytically from first principles! How cool is that? Even though, in theory, one ought to be able to continue with this logic and derive all of chemistry as a simple application of quantum mechanics, it very rapidly becomes too complicated and we must rely on computers.