No one thought to give the transition metals a little more space until Glenn Seaborg and his colleagues at (wait for it) the University of California at Berkeley made over the entire periodic table between the late 1930s and early 1960s. It wasn’t just that they added elements. They also realized that elements like actinium didn’t fit into the scheme they’d grown up with. Again, it sounds odd to say, but chemists before this didn’t take periodicity seriously enough. They thought the lanthanides and their annoying chemistry were exceptions to the normal periodic table rules—that no elements below the lanthanides would ever bury electrons and deviate from transition-metal chemistry in the same way. But the lanthanide chemistry does repeat. It has to: that’s the categorical imperative of chemistry, the property of elements the aliens would recognize. And they’d recognize as surely as Seaborg did that the elements diverge into something new and strange right after actinium, element eighty-nine.
Actinium was the key element in giving the modern periodic table its shape, since Seaborg and his colleagues decided to cleave all the heavy elements known at the time—now called the actinides, after their first brother—and cordon them off at the bottom of the table. As long as they were moving those elements, they decided to give the transition metals more elbow room, too, and instead of cramming them into triangles, they added ten columns to the table. This blueprint made so much sense that many people copied Seaborg. It took a while for the hard-liners who preferred the old table to die off, but in the 1970s the periodic calendar finally shifted to become the periodic castle, the bulwark of modern chemistry.
But who says that’s the ideal shape? The columnar form has dominated since Mendeleev’s day, but Mendeleev himself designed thirty different periodic tables, and by the 1970s scientists had designed more than seven hundred variations. Some chemists like to snap off the turret on one side and attach it to the other, so the periodic table looks like an awkward staircase. Others fuss with hydrogen and helium, dropping them into different columns to emphasize that those two non-octet elements get themselves into strange situations chemically.
Really, though, once you start playing around with the periodic table’s form, there’s no reason to limit yourself to rectilinear shapes.* One clever modern periodic table looks like a honeycomb, with each hexagonal box spiraling outward in wider and wider arms from the hydrogen core. Astronomers and astrophysicists might like the version where a hydrogen “sun” sits at the center of the table, and all the other elements orbit it like planets with moons. Biologists have mapped the periodic table onto helixes, like our DNA, and geeks have sketched out periodic tables where rows and columns double back on themselves and wrap around the paper like the board game Parcheesi. Someone even holds a U.S. patent (#6361324) for a pyramidal Rubik’s Cube toy whose twistable faces contain elements.
Musically inclined people have graphed elements onto musical staffs, and our old friend William Crookes, the spiritualist seeker, designed two fittingly fanciful periodic tables, one that looked like a lute and another like a pretzel. My own favorite tables are a pyramid-shaped one—which very sensibly gets wider row by row and demonstrates graphically where new orbitals arise and how many more elements fit themselves into the overall system—and a cutout one with twists in the middle, which I can’t quite figure out but enjoy because it looks like a Möbius strip.
We don’t even have to limit periodic tables to two dimensions anymore. The negatively charged antiprotons that Segrè discovered in 1955 pair very nicely with antielectrons (i.e., positrons) to form anti-hydrogen atoms. In theory, every other anti-element on the anti–periodic table might exist, too. And beyond just that looking-glass version of the regular periodic table, chemists are exploring new forms of matter that could multiply the number of known “elements” into the hundreds if not thousands.
First are superatoms. These clusters—between eight and one hundred atoms of one element—have the eerie ability to mimic single atoms of different elements. For instance, thirteen aluminium atoms grouped together in the right way do a killer bromine: the two entities are indistinguishable in chemical reactions. This happens despite the cluster being thirteen times larger than a single bromine atom and despite aluminium being nothing like the lacrimatory poison-gas staple. Other combinations of aluminium can mimic noble gases, semiconductors, bone materials like calcium, or elements from pretty much any other region of the periodic table.
The clusters work like this. The atoms arrange themselves into a three-dimensional polyhedron, and each atom in it mimics a proton or neutron in a collective nucleus. The caveat is that electrons can flow around inside this soft nucleic blob, and the atoms share the electrons collectively. Scientists wryly call this state of matter “jellium.” Depending on the shape of the polyhedron and the number of corners and edges, the jellium will have more or fewer electrons to farm out and react with other atoms. If it has seven, it acts like bromine or a halogen. If four, it acts like silicon or a semiconductor. Sodium atoms can also become jellium and mimic other elements. And there’s no reason to think that still other elements cannot imitate other elements, or even all the elements imitate all the other elements—an utterly Borgesian mess. These discoveries are forcing scientists to construct parallel periodic tables to classify all the new species, tables that, like transparencies in an anatomy textbook, must be layered on top of the periodic skeleton.
Weird as jellium is, the clusters at least resemble normal atoms. Not so with the second way of adding depth to the periodic table. A quantum dot is a sort of holographic, virtual atom that nonetheless obeys the rules of quantum mechanics. Different elements can make quantum dots, but one of the best is indium. It’s a silvery metal, a relative of aluminium, and lives just on the borderland between metals and semiconductors.
Scientists start construction of a quantum dot by building a tiny Devils Tower, barely visible to the eye. Like geologic strata, this tower consists of layers—from the bottom up, there’s a semiconductor, a thin layer of an insulator (a ceramic), indium, a thicker layer of a ceramic, and a cap of metal on top. A positive charge is applied to the metal cap, which attracts electrons. They race upward until they reach the insulator, which they cannot flow through. However, if the insulator is thin enough, an electron—which at its fundamental level is just a wave—can pull some voodoo quantum mechanical stuff and “tunnel” through to the indium.
At this point, scientists snap off the voltage, trapping the orphan electron. Indium happens to be good at letting electrons flow around between atoms, but not so good that an electron disappears inside the layer. The electron sort of hovers instead, mobile but discrete, and if the indium layer is thin enough and narrow enough, the thousand or so indium atoms band together and act like one collective atom, all of them sharing the trapped electron. It’s a superorganism. Put two or more electrons in the quantum dot, and they’ll take on opposite spins inside the indium and separate in oversized orbitals and shells. It’s hard to overstate how weird this is, like getting the giant atoms of the Bose-Einstein condensate but without all the fuss of cooling things down to billionths of a degree above absolute zero. And it isn’t an idle exercise: the dots show enormous potential for next-generation “quantum computers,” because scientists can control, and therefore perform calculations with, individual electrons, a much faster and cleaner procedure than channeling billions of electrons through semiconductors in Jack Kilby’s fifty-year-old integrated circuits.
Nor will the periodic table be the same after quantum dots. Because the dots, also called pancake atoms, are so flat, the electron shells are different than usual. In fact, so far the pancake periodic table looks quite different than the periodic table we’re used to. It’s narrower, for one thing, since the octet rule doesn’t hold. Electrons fill up shells more quickly, and nonreactive noble gases are separated by fewer elements. That doesn’t stop other, more reactive quantum dots from sharing electrons and bonding with other nearby quantum dots to form… well, who knows what the h
ell they are. Unlike with superatoms, there aren’t any real-world elements that form tidy analogues to quantum-dot “elements.”
In the end, though, there’s little doubt that Seaborg’s table of rows and turrets, with the lanthanides and actinides like moats along the bottom, will dominate chemistry classes for generations to come. It’s a good combination of easy to make and easy to learn. But it’s a shame more textbook publishers don’t balance Seaborg’s table, which appears inside the front cover of every chemistry book, with a few of the more suggestive periodic table arrangements inside the back cover: 3D shapes that pop and buckle on the page and that bend far-distant elements near each other, sparking some link in the imagination when you finally see them side by side. I wish very much that I could donate $1,000 to some nonprofit group to support tinkering with wild new periodic tables based on whatever organizing principles people can imagine. The current periodic table has served us well so far, but reenvisioning and recreating it is important for humans (some of us, at least). Moreover, if aliens ever do descend, I want them to be impressed with our ingenuity. And maybe, just maybe, for them to see some shape they recognize among our collection.
Then again, maybe our good old boxy array of rows and turrets, and its marvelous, clean simplicity, will grab them. And maybe, despite all their alternative arrangements of elements, and despite all they know about superatoms and quantum dots, they’ll see something new in this table. Maybe as we explain how to read the table on all its different levels, they’ll whistle (or whatever) in real admiration—staggered at all we human beings have managed to pack into our periodic table of the elements.
ACKNOWLEDGMENTS AND THANKS
I would first like to thank my dear ones. My parents, who got me writing, and never asked too often what exactly I was going to do with myself once I’d started. My lovely Paula, who held my hand. My siblings, Ben and Becca, who taught me mischief. All my other friends and family from South Dakota and around the country, who supported me and got me out of the house. And finally my various teachers and professors, who first related many of the stories here, without realizing they were doing something so valuable.
I would furthermore like to thank my agent, Rick Broadhead, who believed that this project was a swell idea and that I was the one to write it. I owe a lot as well to my editor at Little, Brown, John Parsley, who saw what this book could be and helped shape it. Also invaluable were others at and around Little, Brown, including Cara Eisenpress, Sarah Murphy, Peggy Freudenthal, Barbara Jatkola, and many unnamed others who helped design and improve this book.
I offer thanks, too, to the many, many people who contributed to individual chapters and passages, either by fleshing out stories, helping me hunt down information, or offering their time to explain something to me. These include Stefan Fajans; Theodore Gray of www.periodictable.com; Barbara Stewart at Alcoa; Jim Marshall of the University of North Texas; Eric Scerri of the University of California at Los Angeles; Chris Reed at the University of California, Riverside; Nadia Izakson; the communications team at Chemical Abstracts Service; and the staff and science reference librarians at the Library of Congress. If I’ve left anyone off this list, my apologies. I remain thankful, if embarrassed.
Finally, I owe a special debt of gratitude to Dmitri Mendeleev, Julius Lother Meyer, John Newlands, Alexandre-Emile Béguyer de Chancourtois, William Odling, Gustavus Hinrichs, and the other scientists who developed the periodic table—as well as thousands of other scientists who contributed to these fascinating stories about the elements.
Reading Group Guide
THE DISAPPEARING SPOON
And Other True Tales of Madness,
Love, and the History of the World from
the Periodic Table of the Elements
by
SAM KEAN
A conversation with Sam Kean
How did your love affair with science develop?
With mercury. I had a bad go of things in third grade—I came down with strep throat something like a dozen times—and I was clumsy and talked a lot. So whenever my mother put a mercury thermometer under my tongue, as often as not it ended up broken on the ground, and the mercury spilled out. But my mother was very cool about it: she never panicked or evacuated the house; she actually would roll the little spheres of mercury together with a toothpick, and kept the growing bundle in a little jar on a knickknack shelf. I thought it was the most fascinating substance I’d ever seen (partly because I knew how dangerous it was). So I began to read about mercury and follow its connections to other areas of life—alchemy, history, mythology, medicine, and so on.
Why did you choose the periodic table as a focus for the book?
I knew there were great stories out there about elements we never got to talk about in chemistry class (molybdenum, anyone?). And there were hidden and lost stories out there about elements like gold and aluminium that everyone thinks they know so well. The book really just gathered all these stories into one place, to show that the periodic table extends so much farther than most people realize.
So why did tellurium lead to the most bizarre gold rush in history?
Tellurium is the only element that bonds chemically with gold, and the mineral they form looks sort of gold-like, but not quite. It’s a little too yellow, more fool’s good. So when miners in western Australia unknowingly found rocks of the tellurium-gold mineral during one of the maddest gold rushes in history (in the very late 1800s), they threw them away, thinking they were worthless. Some even crushed the rocks and used them as the base for cement to make their homes, or fill in potholes in the street. But word eventually got around that the cement powder actually did have gold in it, which led to people tearing out the potholes and cannibalizing their own homes and hearths. I call it the fool’s fool’s gold rush.
Why did you choose the title The Disappearing Spoon?
The title comes from the story of one element, gallium. It sits below aluminium on the periodic table and looks a lot like it. If you had a hunk of each metal in front of you, you probably couldn’t tell them apart. Except that gallium has one unusual property: it melts at temperatures just above room temperature. It will even soften in the palm of your hand. So it’s sort of a classic nerdy science prank to make a spoon out of gallium and serve it to somebody with coffee or tea—then watch them recoil as the Earl Grey “eats” their utensil. As a title, it really captures the spirit of the book: fun stories that look at science a little cockeyed.
Why is mercury “cultish”?
Mercury wants, desperately, to be around only other mercury atoms, to the point that small bits of the metal crouch into a sphere, to minimize their exposed surface area. That behavior seemed very cultish—only associating with atoms that act the same way, and turning your back on the outside world.
In addition to being a scientist and writer, you also have a master’s degree in library science. Why did you choose that particular subject?
I love libraries and spent some of my happiest childhood hours there. The master’s degree improved my research skills for the book, and I think I would have been content whiling away in a library if I hadn’t pursued writing.
Why did you leave the lab and begin to write a book?
Well, I never worked in a lab full-time. I did have part-time jobs in labs in college and hated them. Scientific work is beautiful when it succeeds but hair-pulling the rest of the time. I just didn’t have the temperament for it. Writing about science lets me keep learning about fascinating things without the frustration of equipment breaking all the time, and I never have to specialize this way, either.
How did you hone your writing skills?
I took to writing whatever I could whenever I could, even if it had little chance of getting published. I’ve got lots and lots of highly polished pieces on my computer that never got read by anyone but interns screening submissions at small magazines, I suppose. (Mind you, most of them probably deserved rejection!) All the rejection was disappointing, of course, bu
t I needed to hone my writing that way.
Tell us about your latest projects.
I’m working on a book about genetics, along the same lines as The Disappearing Spoon. It’s all the funny, peculiar, and scary stories buried in the human genome—retroactive diagnoses of famous people in history, the human race almost going extinct long ago, and so on. I chose the topic because, while we all know that genetics was supposed to transform medicine, the field has taught us so much more than that. It’s revealed such a rich text of human history that we thought was lost forever.
How can we make science more appealing to the next generation of students?
Stories can help, definitely. They’re simply how the mind works—we remember information better if it’s woven into stories, and you can actually learn a lot more science than you’d expect by learning about the strange and wonderful events in science history.
Questions and topics for discussion
What was the most surprising fact you learned from reading The Disappearing Spoon? Were there any elements or scientists you thought you knew a lot about, but then discovered you didn’t?
American science was often viewed as second-rate compared to Europe in the 1800s. What enabled U.S. science to become so powerful in the twentieth century?
Does Mendeleev deserve the credit he gets for “discovering” the periodic table, even though other scientists had the same idea before him?
Sam Kean details numerous prizes awarded to scientists for their discoveries. What do you think are the benefits of awarding prizes for scientific breakthroughs? Can there be drawbacks?
Sam Kean Page 31
