87. Francium: Nothing To Do With Cats

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You don’t have to have a degree to do science, but it helps.

Featured above: This image does not portray what happens when francium hits water, but there are people out there who would try to convince you otherwise.

Show Notes

Hi folks, I know sometimes I take some time to get the show notes and sources posted, but this episode might take even longer than usual. I create this program in my free time, and between personal and professional obligations, there’s precious little of that available right now.

I’ll work on getting the sources in here first, because I think that’s more important. After that, though, I need to devote my attention to radium — an element with many, many stories to tell.

As for francium’s show notes, Dr. Poliakoff can explain a little more about those electrons:

Ah, beans. Toward the end of the episode I mention that Perey was “really, really good at finding astatine.” I should have said “actinium.” (I tend to confuse those two!) Someday, maybe after all the episodes are recorded, I’ll have to go back and amend that in the audio file.

 

Episode Script

The heavier the elements get, the more likely they are to be unstable. To be radioactive, and fall apart at the seams until it’s no longer the atom it used to be.

You could almost say the same thing for the periodic table itself. Here in the table’s final row (so far), the patterns we’ve come to recognize in various chemical groups and neighborhoods start to break down.

For instance: As you descend through the alkali metals, each element reacts much more strongly with water than the last. Lithium floats on water’s surface, fizzing around like a little motorboat until it disappears with a comical pop. Sodium acts similarly, but can also burn with a sputtering orange flame. Potassium floats too, but immediately ignites in a burst of purple, sending sparks flying and ending with a much more considerable bang. Rubidium is the first of the alkali metals that can actually sink in water, but in practice, it’ll almost certainly explode before it can even be fully submerged. And as for caesium, well, Michael Caine would be quite startled indeed by the magnitude of that blast.¹

So naturally you would think that francium, the element at the very bottom of group 1, would be a truly bombastic piece de resistance. And yet, that’s not quite the case. The francium atom is so big — at least, compared to other atoms — that peculiar things start to happen.  Things that Einstein called “relativistic effects.” In essence, its outermost electron travels at such great speed — faster than one third the speed of light — that the usual rules of physics start to break down. Francium actually holds on to its valence electron a little more tightly than caesium does.

Honestly, though, all that’s a bit moot for our demolition purposes anyway. Much like other recent elements, francium is so very rare that collecting a big old chunk of it would be highly impractical, and it’s so highly unstable that even if you could, it would melt your face off well before the sample ever touched the water.

And that sets a pretty good standard for our final lap of the periodic table. The territory may have familiar contours, but we haven’t been here before. Now more than ever, we should proceed with caution.

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

Even though it’s not quite as explosive as caesium, and not quite as rare as actinium, francium does have some notable distinctions of its own. It has the shortest half-life of all the naturally occurring elements — approximately 22 minutes. It’s the largest of all the atoms, although element 119 will probably be bigger if we ever manage to discover it.²

And it was the last element to be discovered outside the lab. Dmitri Mendeleev kicked off the pursuit of the element in 1879 when he predicted the “eka-caesium,” occasionally referring to it as “dvi-rubidium.” Scores of scientists joined the chase, including Horia Hulubei and Fred Allison, but it wasn’t found until 1939.^{3 4}

Actinium had been discovered four decades earlier, partly thanks to work done by the French chemist André Louis Debierne. That is a story for another time — specifically, two episodes from now — but the element held his fascination for the rest of his life.

Actinium is tough stuff to work with. It takes countless hours of painstakingly difficult work to refine even a minuscule sample out of literal tons of uranium ore. It’s the kind of work that a man like Debierne really couldn’t do himself. He was a brilliant researcher, but he pursued multiple studies at any given time. He helped discover that radioactive alpha particles consisted of two protons and two neutrons, for instance, and in collaboration with Marie Curie he had isolated pure metallic radium. So the daily grind of distilling actinium usually fell upon the shoulders of his lab assistant. It’s a bit like how the work made by Jeffrey Koons is only possible thanks to the hard work of dozens of unnamed artists in his Manhattan studio, as we heard about in episode 24. All that while holding prominent administrative positions. For instance, following Curie’s death in 1934, Debierne succeeded her as Director of the esteemed Radium Institute.⁵

But when Marie Curie died, she left behind some of the biggest proverbial shoes to fill in all of science, and she had successors biological as well as spiritual. Her daughter, Irène Joliot-Curie, was a brilliant chemist in her own right, and had little difficulty carrying a baton that many would have found burdensome. Many of actinium’s properties were yet unknown when Marie died, including the precise length of its brief half-life. Irene worked tirelessly to catalog these attributes.⁶

Working with exceptionally pure samples of actinium, prepared to highly exacting standards, an anomaly became apparent: Following the isolation of a sample of actinium, the sample’s radioactivity would sharply and constantly rise until it finally leveled off after about two hours. Noticing this phenomenon required working with a nigh-unadulterated sample of actinium; otherwise, radiation from various contaminants would hide the signal in the noise. And that was what led to the discovery of element 87, a daughter product produced after element 89 releases an alpha particle.

Now, Joliot-Curie was only half Debierne’s age at the time, but she had a lot going on, too. On top of performing Nobel-winning research, she did important medical work, became one of the first women to hold an official position with the French government, and raised a third generation of little geniuses in Hélène and Pierre Joliot-Curie. So when she shared the news of this discovery with Andre Debierne, her old colleague and family friend, she was actually reporting on the grunt work performed by her lab assistant. Nothing wrong with that, it’s really just the nature of how this sort of work gets done.

In fact, Debierne must have found this whole conversation rather amusing, because all these heretofore-undiscovered secrets of actinium were old news to him. Entirely coincidentally, his lab assistant had recently made the same discovery in the course of performing research for him!

That might sound like the kind of conflict that underlies some of the most bitter, longstanding feuds in the history of science. And indeed, this was a terrifically awkward situation — but not because they had each independently discovered a new element. No, what they independently discovered in that moment was that, entirely unwittingly, they had both been assigning work to the same lab assistant.

Her name was Marguerite Perey, who by not-quite-thirty years old was already one of the leading minds on the fledgling study of radioactivity, much like Harriet Brooks and the Curies themselves. Apparently, in the prior decade, she had simply never mentioned to either of her bosses that she was also working for the other one. Reportedly, upon making the realization, any amusement Debierne may have felt quickly gave way to a rather embarrassing fit of rage. Eventually — presumably after a lot of indignant muttering — the decision was made that neither Debierne’s name nor Joliot-Curie’s would appear alongside the discovery’s announcement. This one belonged solely to Marguerite Perey.⁷

And rightly so. On top of all the elbow grease, she possessed a greater practical understanding of actinium than probably anyone else on the planet. The woman had done so much work with radioactibity that she could have presented a doctoral thesis on the subject. Literally! Not only that, but she probably could’ve earned some very distinguished medals and prizes, too! There was just one problem: Aside from a technical certificate she had earned ten years earlier, Perey had no scientific bona fides — not even a bachelor’s degree.

That’s a lot of work to catch up on — it’s a little harder than scrambling to finish next period’s algebra homework during recess. So it took several more years, but she finally earned her PhD and returned to the Radium Institute as a senior scientist. She later chaired the University of Strasbourg’s nuclear chemistry department, served as a member of the Atomic Weights Commission, and was nominated five times for a Nobel Prize. Alas, always a nominee, never a laureate, but for once on this program, that actually seems like the lesser injustice.

You might wonder why element 87 is named after France when gallium already took its name from the country’s Latinized name, and lutetium did likewise with the Latin name for Paris. Even for the 1930s, it feels just a little bit francocentric.

Perey thought so too, it seems, because she wanted to give it the name catium. She thought that francium’s position on the periodic table was interesting — not only is it at the bottom of group one, but no element is more distant from fluorine. And just as fluorine will form negative anions more… enthusiastically than any other other element, element 87 is tied with caesium for how violently it will react to form a positive cation.

Irene Joliot-Curie advised against this name, because she believed that the English-speakers of the world would think it had something to do with domestic felines. Since (to my great dismay) no such connection exists, they went with the well-established nationalist backup.

Perey should be something of a role model for us element hunters. Her entire career was founded on being really, really good at collecting astatine. But you probably don’t want to comb through a house-sized lump of uranium ore just to gather a few errant atoms of francium. There are a few other familiar options, like seeking out esoteric radiochemical medications or pulling the old “I’m-sure-there’s-an-atom-or-two-of-francium-somewhere-in-this-lump-of-granite” trick, but for the discerning — and ambitious — collector, there is another way: Synthesis!

By performing a little chemical arithmetic using common household materials, we can fuse our way to a sample of francium. In 1995, the State University of New York pioneered just such a technique. All you’ll need is a bit of gold from an old piece of jewelry or electronics and some breathable air. Take oxygen atoms from the breathable air — that’s element 8 — and slam them into the gold — element 79. Seventy-nine plus eight equals eighty-seven — tada! Vive la France!

Just  a couple minor issues of which I am sure you are already well aware: Due to francium’s very brief half-life, your sample would be gone by the end of the day. You could always make more, except for the second problem: you’ll need to get your hands on a linear particle accelerator. The price of those things has really come down over the past hundred years, but they still start around half a million dollars. (I hear you can get a Basic Varian 21/23 series for as low as $175k, if you’re lucky.)^{8 9}

I don’t have demographic data on the listenership’s average annual income, so you all might have that kind of cash underneath your couch cushions, for all I know. If not, then you’ll need to first discover a way to add several hundred thousand dollars your collection. For advice on that particular subject, you’ll probably want to find a different podcast.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn more about the strangeness of francium’s speedy electrons, visit episodic table dot com slash F r.

Next time, we’ll meet radon’s “emanant” progenitor, radium.

Until then, this is T. R. Appleton, reminding you that if you work with someone for nearly a decade, maybe make an effort to get to know them a little better.

1. Chemistry School, Reactions Of Group 1 Elements (Alkali Metals) With Water.
2. ThoughtCo., Francium Facts. Anne Marie Helmenstine, November 4, 2019.
3. Elementymology and Elements Multidict, Francium. Peter van der Krogt.
4. Museum Of Radium And Radioactivity, The Discovery Of Francium. Bertrand Goldschmidt, 1990.
5. Oxford Reference, André Louis Debierne.
6. Encyclopedia.com, Joliot-Curie, Irène (1897-1956). Karin Haag.
7. Encyclopedia.com, Perey, Marguerite (1909-1975). John Haag.
8. Radiology Oncology Systems, Linear Accelerator (LINAC) Price Guide & Costs.
9. Tree Hozz, How Much Does A Linear Accelerator Cost?