If you've learned all the elements from actinium to zirconium, it's time to head back to the periodic table, where there's a new, extremely heavy element in town.
The new element doesn't have an official name yet, so scientists are calling it ununpentium, based on the Latin and Greek words for its atomic number, 115. (Related: Read a feature on element hunters in National Geographic magazine.)
In case you forgot your high school chemistry, here's a quick refresher: An element's atomic number is the number of protons it contains in its nucleus.
The heaviest element in nature is uranium, which has 92 protons. But heavier elements-which have more protons in their nucleus-can be created through nuclear fusion. (Related: Learn how to make an element.)
The man-made 115 was first created by Russian scientists in Dubna about ten years ago. This week, chemists at Lund University in Sweden announced that they had replicated the Russian study at the GSI Helmholtz Center for Heavy Ion Research in Germany.
Element 115 will join its neighbors 114 and 116-flerovium and livermorium, respectively-on the periodic table just as soon as a committee from the International Union of Pure and Applied Chemistry (IUPAC) decides on an official name for 115.
We asked Paul Hooker, a chemistry professor at Westminster College in Salt Lake City, Utah, for his take on the latest addition to the periodic table.
So it sounds like 115 was actually created ten years ago, by a lab in Russia. Why are we just learning about its discovery?
When you find a new element, it has to be confirmed. You need two different labs to confirm it before [IUPAC] considers adding it to the periodic table.
This is the second lab coming in and repeating the same experiment, so now it's considered to be an official new element.
So what did the Russian and Swedish chemists actually do?
The way that you make new elements now is by shooting a beam of an element at another element and then seeing what happens when they collide.
In this case, the researchers used americium, which is kind of interesting because it's an unstable, radioactive element. They fired calcium atoms-which are much lighter than americium atoms-at the americium for weeks or even months. Most of the calcium atoms bounced off, but every now and then the atoms collided and instead of the calcium element bouncing off, it actually stuck to the americium element. When that happens, you get a short-lived atom with more protons in its nucleus, which is the center of the new element 115.
How did they know they created a new element if it happened so quickly? I think I read that it existed for less than a second before it decayed.
They look for the decay products. They look for telltale signs for when 115 disintegrates, by what's called alpha particle emission. When they see enough of those signals, they can say they probably formed a new element.
How do they know if a new element will be unstable or not?
There was an element 118 that was predicted to be much more stable; 115 wasn't predicted to be especially stable. We know what is stable. Certain ratios of protons to neutrons are stable. As the nucleus gets bigger and bigger, it's not stable-and then it can radioactively decay and spit out smaller particles-that means it's really not very stable.
Can anyone try to create a new element?
No. You need a large vacuum chamber because you can't fire calcium atoms through the air. You need a lot of specialized equipment. There aren't many labs that can do this type of thing. The only people interested in doing this are trying to answer some of the bigger questions, like "How is all matter held together?"
Where are most new elements created?
Most of these new elements have been formed in Russia and the States for the past 30 to 40 years. It's become a race for who can get the next new element, to try to make the biggest one you actually can. But of course, because they're so big, they're very unstable and fall apart extremely quickly.
If they fall apart extremely quickly-and clearly don't exist in nature-then what's the point?
I talk about this a lot with my students. I basically tell them, "Because it's there." There's no way that a new, unstable element is going to have any uses because it deteriorates so quickly. But it gives insight about the forces that hold atoms together so we can learn more about how the universe is held together.
Why are people really doing this? Why do we send particles through huge colliders? Why are we smashing things into each other at higher and higher velocities? I think it fulfills the human race's natural curiosity. We want to know where we come from. And every time we answer something, we come up with ten more questions to answer.
This was a man-made element. How do we know we've found all of the naturally occurring elements?
The good thing with elements is that they're defined by atomic numbers, meaning they're defined by the number of protons in the nucleus. This number is never a fraction, so you can't have, say, 3.2 protons in a nucleus. So we know we have them all because we know of an element with one proton and an element with two protons and so on.
Is there a limit to how many elements we can create?
Well, we're hitting a limit with stability when there are over 90 protons in a nucleus, so while we may find more, we're certainly not getting up to 1,000 protons. It would be too unstable.
One last question: I actually have a periodic table shower curtain. Do you recommend getting an updated one?
I recommend updating your shower curtain when 115 is confirmed. When the committee gets together and names it. And that's an entirely different question.
So I guess I should ask: Why does a committee do it?
Because these things get quite political. Back in the day, the Americans would say: We discovered it and named it something. The Russians would say: We did, and named it something else. So a committee has to get together and negotiate. They try to keep it apolitical-maybe they'll name it after someone from Italy or Lithuania or something.