What’s at the end of the periodic table? — Speaking of Chemistry

What’s at the end of the periodic table? — Speaking of Chemistry


Laura Howes: I recently visited these massive
magnets at the GSI in Darmstadt, Germany. They’re so big I had a hard time getting
them in the frame of my video. Matt Davenport: Dang. Those are pretty big. And what are they used for? Laura: Well, GSI operates a particle accelerator,
and one of the facility’s goals is to make and study new atoms. The magnets are part of the Separator for
Heavy Ion Reaction Products, or SHIP. Fun fact, the researchers picked SHIP as a
nod to the dream of sailing to the island of stability. So, let me back up for a second. All of the synthetic elements—elements higher
up on the periodic table, higher than uranium—are unstable. They are radioactive. Matt: And most of them don’t live that long
before they decay. Laura: But there is a theory that if we keep
making bigger atoms, some of them will be stable. A little cluster, or island, amid the sea
of unstable elements. Matt: We’ve completed seven rows of the
periodic table without hitting that island’s shores, but scientists are still looking. Laura: Right. And one approach is to keep making brand-new
elements by adding protons to the nucleus. But we’re going to look at the other approach,
which is adding more neutrons to existing superheavy elements. Matt: Yep, and that poses some interesting
questions. Namely, what are we hoping to learn from and
about the superheavies? Laura: And what are the prospects of making
more stable versions to make that research easier? Matt: And we’ll talk about the rad superheavy
chemistry that folks are already doing, when they have just a few atoms that exist for
mere moments. So, where should we start, Laura? Laura: What about the nucleus? Matt: Oh, good call. That’s where everything starts, right? If you want to do chemistry on superheavy
atoms, you would prefer that they stick around. Laura: Yep. And that requires a nucleus with some semblance
of stability. Matt: As we alluded to earlier, the superheavies
don’t last too long. Laura: We’re usually talking in the neighborhood
of microseconds or milliseconds. But some are longer. Seaborgium, for example, can last closer
to 30 s. Matt: And that lifetime really depends on
the isotope that you’re talking about. Isotopes are versions of the same element
with different numbers of neutrons. And some of the yet-to-be made isotopes of
superheavies could be super interesting. I learned about this from Witek Nazarewicz,
who does computational studies of nuclei at Michigan State University. You’re not the only one who got to go on
a field trip. Laura: But did you get to see a large particle
accelerator facility? Matt: I did. It’s just not open yet. But soon. Laura: Doesn’t count. Matt: Fine. You win this round. At any rate, nuclear physics is [mind-blowing
sound], but let me drop the basics on you. The nucleus has protons and neutrons, right? You want a healthy balance of both. Too many of either, and your nucleus is going
to fall apart. So sayeth nuclear physics. That’s what these two lines in Witek’s
chart tell us. Left of this left line, you’ve got too many
protons. To the right of the right line, you’ve got
too many neutrons. But in between is fair game. Now, let’s look closer at the superheavies. The colored spots are what scientists have
made. Witek Nazarewicz: So this is the limit of
current research on superheavy elements. Matt: All of that territory between the two
lines are isotopes waiting to be made. And some of those isotopes could be really
long lived. Witek Nazarewicz: And this is a humbling picture
because it shows you that we’re exploring a little forgotten corner of nuclear landscape. The territory of superheavies is much greater
than that. Matt: Here’s where the other shoe drops. Laura: It is really, really hard to make new
isotopes. Witek Nazarewicz: For theorists, it’s very
easy to make such predictions and be happy. For experimentalists, the challenge to go
by one unit up or one unit to the right . . . it can be years. But who says that this game is fair? Matt: We’ve actually made an entire podcast
about how hard it is to make these things, right, Kerri? Kerri Jansen: We sure did, Matt. We’ve got a link in this episode’s description. Matt: But the fact remains, we can synthesize
superheavy isotopes. Laura: Yeah. So that’s one of the things they do at the
GSI in Darmstadt. Let’s walk through the science real quick. To make superheavies, researchers use a particle
accelerator. This fires a beam of particles—say, calcium
ions—at a heavy-element target. Plutonium or americium, for instance. But keep in mind, from the nuclear synthesis
perspective, that target atom and the ion beam are mostly empty space. To the average person, though, these targets
are thin bits of film that look pretty solid. But on the scale of atoms, I assure you, we’re
dealing with mostly empty space. Matt: So your beam has a super-teensy probability
of hitting the target. Laura: Right. Or you get a glancing blow instead of a head-on
collision that you need for the ion and element to fuse, forming a whole new isotope. And when you finally do get them to fuse,
the resulting isotope might be so short lived, it’s gone before you can do anything with
it. Matt: That all sounds impossible. How does any superheavy research get done? Laura: Slowly. Christoph Düllmann: At the GSI, we typically
now conduct experiments that bring you useful results within a time frame of say, 2–4
weeks. In the time frame of roughly 1 month, we expect
the observation of several atoms. Laura: That’s Christoph Düllmann, head
of the superheavy-element chemistry department at the GSI. Matt: To recap, then, they work for like a
month to get, let’s say eight atoms to study? Not to put too fine a point on it, but I feel
like we should touch on why someone would want to do superheavy-element chemistry. Laura: Good point. One of the big things is that the superheavies
are drawing focus on how we’ve arranged the periodic table. Matt: Which is periodically, right? Laura: About that. It turns out scientists
are still debating the best way to arrange everything. Right, Sam? Sam Lemonick: Totally. You can read more about that in a feature
I wrote. We’ll add a link to it in the description. Laura: And the chemistry of the superheavies
is factoring into those discussions. For example, oganesson, element 118, is in
the noble-gas group, but it may behave more like a semiconductor, according to recent
computational modeling. Matt: So it’s almost like an identity thing
for superheavies? Like, “I’m not like the others in my group. Where do I belong?” Laura: I’m not sure they really care,
but questions about periodicity are a big deal for the periodic table. And Christoph Düllmann says there are exciting
questions beyond that as you make more stable elements. Christoph Düllmann: We can do more benchtop-style
experiments and study much more profound properties. And that’s fantastic, and eventually if you
make enough of that, you will find applications. Laura: For example, remember I mentioned that
seaborgium can have a longer lifetime? It’s long enough to actually do chemistry. The isotope can merge with ligands to form
a hexacarbonyl compound. Matt: That is wild. But most superheavies don’t live that long,
right? Laura: No, other superheavies only last long
enough for gas-solid chromatography, which can measure the reactivity of the elements. Matt: I’ve heard of chromatography, but
the kind I’m thinking about takes longer than a millisecond to run. How does it work with these short-lived isotopes? Laura: The moment an atom is created, it is
fired down an array of detectors. A postdoc in Christoph’s group called Lotte
Lens showed me what those detectors look like, but she didn’t want to be on camera. Matt: Oh, that’s too bad. Laura: But she did explain to me that by measuring
where the atom adsorbs on the detectors, she she can calculate the reactivity of the atom. Researchers can then compare that to theoretical
predictions. Christoph Düllmann: We get good guidance
from theory. And this is always helpful. The experiment is designed to answer a specific
question. Laura: And that’s not all. Aside from gas chromatography, scientists
are developing different forms of spectroscopy to study the superheavies too. Matt: It sounds like scientists are working
on this problem from a couple different angles, then It’s not just, “Let’s make more atoms
of more stable isotopes.” It’s also, “Let’s make better gear to
study what we can already make.” Laura: Sure. But let’s not kid ourselves. More atoms of stable isotopes is the
goal. And Christoph thinks that island of stability
might still be out there, even if the elements aren’t superstable like those higher up
on the periodic table. Christoph Düllmann: So the picture of the
island of stability is, in my opinion, fully correct. We do not know where the center is, we do
not know how high the mountain or this peak of stability really is. We’re at the shoreline more or less. And so we start to climb up the hill and find
more long-lived isotopes. Laura: I like to think of these researchers
as explorers. So they’re looking for the island of stability,
and it might not have superstable elements there, but they might find some interesting
things or something different, and I’m excited about that. Matt: Yeah. And, either way, we got to go look at some
pretty sweet equipment. Laura: And you got to wear a hard hat. Matt: That may have been the best part of
this. Joking aside, we want to know what you’re
most excited to learn about the superheavy elements. Let us know in the comments. Laura: This video is part of C&EN’s celebrations for the International Year of the Periodic Table. Make sure to visit our website to see all
of the other awesome content we’ve produced this year. Matt: Including an awesome story that you
wrote with even more superheavy goodness. Laura: Thanks for watching.

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3 thoughts on “What’s at the end of the periodic table? — Speaking of Chemistry

  1. Ain't it so beautifull to still find good content like this nowadays? Recently I've been reading an article telling the history of the periodic table and discovery of elements. I'm pretty sure that as Mendeleiev hit the nail on the head with his previsions, our scients we'll do for next elements too!

  2. Could someway, at least theoretically, be possible to technollogically interfere with bosonic fields or nuclei charges/forces to somehow get to slow down and stabilize those heavier element nuclei to increase their half life and size?

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