61. Promethium: What A Friend We Have In Prometheus

We’ve met mythological light-bearers before, but this one possesses a decidedly nobler spirit.

Featured above: A very cool-headed Prometheus getting relieved by an equally chill Heracles. For being dead, the Nemean Lion is impressively modest.

Show Notes

I’d ordinarily say that so-and-so deity created “humanity,” but in this case, Prometheus really did only create man. Zeus punished men for Prometheus’s fire theft by having Hephaestus create an incredibly beautiful human, then having Hermes give it “a deceptive heart and a lying tongue.” Voila, woman was born.

And not just any woman — this was Pandora. She hung out with Prometheus’s brother, Epithemeus (whose name means “hindsight,” incidentally) and they got into all that trouble with the jar and the demons and hope and whatnot.

Really, all the old Greek myths are… problematic by our modern sensibilities. For instance, regarding that “deviant congress,” if you’re unfamiliar, just look up “Leda and the Swan.” But not if you’re on a library computer, or if your boss might glance over your shoulder.

As far as Hephaestus, he didn’t really seem to mind that Prometheus nabbed his burning ember. He expressed sorrow at doing the task he was assigned. From Aeschylus’s play, Prometheus Bound:

Against my will and yours, I must bind you

with chains of brass which no one can remove

How much I hate the work I do!”1

Seems like everyone else on Olympus was pretty chill, but Zeus was a real buzzkill.

Speaking of Zeus, most interpretations of the Greek texts seem to agree that he sent an eagle to harass Prometheus, rather than a vulture. It’s not complete unanimity, though, and the chemists who named promethium mentioned a vulture, so I ran with that.

Aeschylus seems to have written two other plays about Prometheus, too, including at least one that mentions his exploits after being freed by Heracles. Sadly, those works were almost entirely lost, so who knows what he’s up to?

Moseley was quite young when he drew his conclusions about atomic number. He almost certainly would have won a Nobel Prize, and could’ve contributed to chemistry for decades afterward, had he not joined the army in WWI. He was killed at Gallipoli by a sniper’s bullet.

Episode Script

Humanity was never held in very high esteem by the gods of ancient Greece. We witnesses harsh judgement rendered upon Niobe twenty episodes ago, and that was a fairly typical interaction between god and mortal. At best, the Olympians saw humans as acceptable companions for the occasional evening of inebriated and deviant congress.

Just about the only one who was on our side was Prometheus. To be fair, you would hope he’d have a soft spot for humans. Prometheus created man by molding him out of clay.

It took a few millennia for us to get around to it, but humanity repaid the consideration in the 1940s when scientists isolated and named element 61, the fifteenth and final lanthanide.2

You might recall that the other lanthanides were discovered in the 19th century. They were all difficult to isolate, due to their similarity to each other, but there’s a reason promethium’s discovery was even more difficult: All of its isotopes are highly radioactive, and it essentially can’t be found in nature. Like technetium, it couldn’t be studied until it was synthesized in a laboratory.3

There’s kind of a nice symmetry there, suitable to its mythological origins: Prometheus created man — and man created promethium.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re bound to learn something about promethium.

No one would have gone looking for promethium if it weren’t for the periodic table. At least, once Henry Moseley got his hands on it.

Early incarnations of the periodic table were arranged in order of increasing atomic mass, but that was frustratingly imperfect. Cobalt, for instance, is slightly heavier than the element that comes after it on the periodic table, nickel.

Moseley found a way to measure the electrical charge of an element, and showed that this charge increased by a constant amount as you moved from one to the next. For example, iron displayed 26 units of charge, cobalt 27, and nickel 28. Later research would show that this charge corresponded with the number of protons in an atom’s nucleus, and this was a very big deal. He had found an empirical measurement, dubbed the “atomic number,” which aligned with observed behavior, solved the problem of “pair reversals,” and generally made the periodic table very tidy.4 5

So tidy, in fact, that it uncovered some gaps in the table. There were several spaces where an element would fit which for which no known element existed. Atomic number 43, for example, was unknown — which makes sense, because that’s the atomic number of technetium, the first element discovered by synthesis in a lab.6 7

Atomic number 61 was another of these blank spaces, revealing the existence an element that would otherwise have gone unnoticed. So the periodic table became more than just a record of chemistry’s knowledge, but also an instrument of discovery.

Element 61 thus revealed, it was only a matter of who would be clever enough to find it.

Prometheus was a rather clever fellow, himself. His name means “foresight,” and that was a trait he had in spades.

For one thing, he wasn’t actually a god in the same way Zeus and Hera were. He was one of the titans, the generation of immortals who preceded the Olympian gods. Predictably, there was some strife between old and young, and soon it was a matter of all-out war.

Forward-thinking Prometheus recognized that the young’uns were probably going to emerge victorious, so he teamed up with Zeus in that war. He was right, of course, and for his service, Prometheus was allowed to stick around Mount Olympus. Meanwhile, his titan siblings were banished to an infinite abyss of suffering called Tartarus.

It was around that time Prometheus created humanity, but his work was subject to some restrictions imposed by his new best bud, Zeus. These humans were to be mortal and subservient to their superiors. Zeus allowed Prometheus to choose how they would show their piety.

Prometheus slaughtered a bull and divided it into two bowls. One contained all the choicest cuts of the animal, but he covered them in the bull’s intestines and other organs. The other bowl was full of bones hidden beneath a thick layer of glistening fat.

He then asked Zeus which of these should be offered to the gods, and which the humans could keep for themselves. Zeus chose the bowl topped with rich fat, believing it was the finer option, while the humans would subsist on the miscellaneous unappetizing odds and ends.8

Only after the decision had been made did Zeus realize he’d been tricked into choosing a bowl full of bones. Because of Prometheus’s little ruse, humanity would burn the bones and fat of animals as sacrifice to the gods, and keep the most delicious cuts of meat for their own enjoyment.

Zeus was furious. He couldn’t undo what had been done, but retaliation was fair game, apparently. He took fire away from humanity. Prometheus’s creation could no longer use it to cook or for anything else. There were dark days ahead.

Back in the twentieth century, the outlook was also bleak for scientists on the trail of element 61.

Scientists pursued the element as early as 1912, but they found very little. A desire for results often outpaced any empirical evidence. In 1924, Italian chemist Luigi Rolla recorded the uncertain conclusions of his spectrographic analyses, sealed them in an envelope, and handed them over to a university for safekeeping.  The idea was, if anyone else announced a discovery along the same lines, Rolla could pop up and say that he had actually made the discovery first.9 10

Sure enough, two years later a team from the University of Illinois claimed that they had found spectrographic evidence of element 61, and they suggested the name “illinium.”11

It was exactly the contingency that Rolla had prepared for. He ran back to the university and caused a great commotion, convening an audience for a grandiose announcement: “The element sought in vain for so long, the rarest of the rare earth elements would have to repeat, by saying its name, the name of that most Italian of Italian cities, where Dante expressed the spirit of our race. For this element, atomic number 61, we propose the name of florentium and the symbol Fr.”12

Elsewhere, scientists weren’t so convinced that anyone had actually succeeded in finding the element. Doubt cast a long shadow over these announcements, and for nearly twenty years, no one was able to replicate their results. They couldn’t have — it was impossible. Rolla and the Illinois team were looking at mineral samples, but just like with technetium, any naturally occurring promethium on earth would have decayed into something else millions of years ago.13 14

Other scientists tried novel approaches. One team at Ohio State University might have actually been successful in synthesizing a sample in 1938. They had performed their research with a cyclotron, and thus proposed the name “cyclonium,” but their evidence was more circumstantial than direct, and by this point the community was even more skeptical than usual. It was like the fable of the boy who cried “wolf” — by this point, anyone who announced a discovery of element 61 would have to stand up to intense scrutiny.15

Speaking of fables, we should check back in on our friend Prometheus.

He was anguished to see his children suffering in the cold and the dark. He even felt some level of responsibility — it was his trick that compelled Zeus to confiscate fire from humanity.

So he took it upon himself to make things right. He climbed Mount Olympus and snuck into the workshop that belonged to Hephaestus, god of the forge. There, he took a smoldering ember and hid it within a hollow stalk of fennel. He returned to Earth and gave humanity the gift of fire. Once again, they could cook their food, light their paths, and warm their homes. Prometheus had carried the spark that allowed humanity to light the fire of civilization.16

But civilization makes a lot of noise, and eventually Zeus noticed what Prometheus had done. He was furious, and this time, Prometheus would personally pay the price for his offense.

Zeus ordered Hephaestus to take Prometheus to the Caucasus mountains and chain him to the rocks, where he would remain for all eternity. Exposed to the elements, his body would be burned by the sun during the day and covered with frost overnight. Worse yet, a vulture would descend upon him and eat his liver while he writhed in pain. At night, his wounds would heal, and his liver would grow back, only for the vulture to return and devour it again — every single day for all eternity.17 18

It’s hard to imagine a punishment more torturous than that, but he never showed any regret for what he had done. Unlike the other tempestuous immortals of Greek mythology, Prometheus was always on the side of humanity. He’s been revered throughout the ages for his compassion and empathy, and as a bringer of light, he often appears in art and literature as an embodiment of scientific inquiry.19

It’s most fitting, then, that he should be honored with a position on the periodic table of elements, but element 61’s eventual discovery was marked by a surprising lack of fanfare. It was a group of scientists at Oak Ridge National Laboratory who finally provided incontrovertible proof of the substance in 1945 while sifting through nuclear waste from the Manhattan Project.20

Scientific work was especially clandestine at the time, so it would actually be two whole years before the discovery was announced to the public. When that announcement finally was made, it was only as part of a modest article published in the Journal Of The American Chemical Society.21

For a while, it was merely called “Element 61.” A handful of names were proposed, including — perhaps in jest — “Grovesium,” after General Leslie Groves, the man in charge of Oak Ridge whom we met in Episode 47, Silver.

It was Grace Mary Coryell, wife of one of the discoverers, who proposed the winning name, inspired by the exploits of our mythological hero. The team explained,22 23 24

This name not only symbolizes the dramatic way in which the element may be produced in quantity as a result of man‘s harnessing of the energy of nuclear fission, but also warns man of the impending danger of punishment by the vulture of war.”25

Since the element was christened, up to the moment of this episode’s original broadcast, humanity has so far managed to keep that vulture at bay. These have been trying times, but hopefully that won’t change.

As for Prometheus, things turned around for him eventually. After however many days of eternity, Heracles, son of Zeus, happened upon Prometheus on the way from one Labor to the next. In exchange for some valuable information, Heracles broke the chains that bound Prometheus to the rocks.

Perhaps there’s some poetic resonance, then, in the fact that you will never find promethium in any rock from this planet. But that doesn’t spell doom for your element collection. While all of its isotopes are radioactive, they’re stable enough for synthetic samples to find some highly esoteric uses.

For a while, that radioactivity was exploited to fuel pacemaker batteries. Promethium regularly emits a beta particle — which is simply an electron — and that would strike a phosphor, emitting light that could be converted to electricity. This never saw very widespread use, partly because the battery had a relatively short lifespan, and partly because folks weren’t too keen on the idea of a radioactive heart.[NOTE]Thomas Jefferson National Accelerator Facility – Office Of Science Education, The Element Promethium.[/note]

Promethium can be used to create luminous paint, especially useful for meters and dials that need to be read in dark places. You might be able to find an old luxury compass or diving watch that has promethium numbers on its face, although it’ll cost a pretty penny. If you’re really well connected — like, feloniously well connected — you might get your hands on a real piece of history: control panels and electrical switches in the Apollo Lunar Module and the moon buggy were illuminated with promethium paint.26 27

That would certainly be a prize for your collection, and how appropriate for this particular mythological figure to be represented by a luminous object — one created as a consequence of one great scientific endeavor in the pursuit of yet another.

So if you can, stock your element shelf with one of those radiant objects, and leave a light on for Prometheus.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn what Hephaestus thought about having to nail his fellow immortal to a mountain, visit episodic table dot com slash P m.

Next time, we’ll mix with samarium.

Until then, this is T. R. Appleton, reminding you that bones with fat sounds kind of like ossobuco, so I don’t know what Zeus was complaining about.


  1. Prometheus Bound, Aeschylus (translated by Herbert Weir Smyth).
  2. Chemicool, Promethium. Doug Stewart, October 18, 2012.
  3. A Guide To The Elements, p. 153 – 154. Albert Stwertka, 2002.
  4. Chemistry World, Promethium. Brian Clegg, December 16, 2008.
  5. Nature In Your Element, Promethium Puzzles. Stuart Cantrill, 2018.
  6. American Scientist, Master Of Missing Elements. Eric Scerri, September-October 2014.
  7. De Gruyter, Henry Moseley And The Search For Element 72. K. M. Frederick-Frost, April 1, 2019.
  8. Encyclopedia Britannica, Prometheus. Last updated February 6, 2020.
  9. Chemistry And Chemists In Florence: From The Last Of The Medici Family To The European Magnetic Resonance Center, p. 73-74. Marco Fontani, Mary Virginia Orna, and Mariagrazia Costa, 2016.
  10. Handbook On The Physics And Chemistry Of Rare Earths, p. 64-67. Elsevier, 2010.
  11. Elementymology And Elements Multidict, Promethium. Peter van der Krogt.
  12. Chemistry And Chemists In Florence: From The Last Of The Medici Family To The European Magnetic Resonance Center, p. 73-74. Marco Fontani, Mary Virginia Orna, and Mariagrazia Costa, 2016.
  13. Royal Society Of Chemistry, Promethium.
  14. Los Alamos National Laboratory, Promethium.
  15. Handbook On The Physics And Chemistry Of Rare Earths, p. 66-68. Elsevier, 2010.
  16. Ancient History Encyclopedia, Prometheus. Mark Cartwright, April 20, 2013.
  17. You might think that’s a hell of a long time. Personally, I think that’s a hell of a bird.
  18. Prometheus Bound, Aeschylus (translated by Herbert Weir Smyth).
  19. Just as an example, Percy Shelley’s preface to his book, Prometheus Unbound: “…Prometheus is, as it were, the type of the highest perfection of moral and intellectual nature impelled by the purest and the truest motives to the best and noblest ends.”
  20. PubChem, Promethium. National Center For Biotechnology Information.
  21. Journal Of The American Chemical Society, The Chemical Identification Of Radioisotopes Of Neodymium And Of Element 61. J. A. Marinsky et. al., 1947.
  22. Nature, Promethium, The New Name For Element 61. July 31, 1948.
  23. Royal Society Of Chemistry, Promethium.
  24. Encyclopedia Britannica, Promethium. Last updated January 24, 2018.
  25. StuartCantrill.com, Promethium Unbound. Stuart Cantrill, November 21, 2018.
  26. The History And Use Of Our Earth’s Chemical Elements: A Reference Guide, p. 286 – 287. Robert E. Krebs, 2006.
  27. PeriodicTable.com, Promethium. Theodore Gray.

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