Blogging the Periodic Table

Promethium: Uranium Stole Its Fire
Each one has a story.
July 22 2010 7:00 AM

Blogging the Periodic Table

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Illustration by Alex Eben Meyer.

A century ago, so few natural elements remained undiscovered, and so many scientists were scouring the Earth for the honor of finding them, that disputes over who discovered what first became commonplace. Scientists repeatedly shot down false claims, and acrimony could linger for years, even on a national level. In one dispute between French scientists and a team of Danish and Hungarian scientists, a French magazine sniffed that the whole thing "stinks of Huns," as if Attila himself had discovered the element.

By the mid-1940s, just one box remained open among the natural elements on the periodic table, Element 61. But after all the strife over earlier claims, the announcement of this one's discovery, in 1947, was strangely anticlimactic. Three scientists from Oak Ridge National Laboratory made the announcement at a scientific meeting that year—but revealed that they'd actually discovered it two years before and had sat on it. They had said nothing partly because of security restrictions at a national lab, but they also knew the delay wouldn't matter: No one else was looking for the element. The media gave the announcement unenthusiastic coverage, calling the new element "not good for much." Science had at last discovered the final natural element, completing the periodic table after almost a century of work, and few seemed to care. What happened?

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Uranium and plutonium happened. Uranium was not new at the time but had newly discovered properties. A French chemist (invalidating a premature claim by a German one) had actually isolated pure uranium way back in the 1840s. But it remained little more than another metal until 1896. That year, Antoine Becquerel discovered radioactivity while experimenting with uranium salts. Then, an Austrian-German team announced in 1939 the discovery of uranium fission—that uranium atoms can split and start a self-sustaining and highly explosive chain reaction. Even without a world war looming, uranium would have become the most exciting element on the table. With the war, it became the only element worth bothering over.

Unlike uranium, plutonium was created in an American lab, in 1940, but scientists soon realized that it could produce even wilder chain reactions and even bigger explosions. In fact, fearing another country would create it, too, the American government went to great lengths to keep even the existence of plutonium a secret. Plutonium is the 94th element, and the most desirable kind for a bomb is plutonium-239. So some scientists from California who worked with the stuff on the Manhattan Project decided to call their intramural baseball team the 49ers. The government immediately vetoed the name as a security risk. Plutonium was that important.

All of which is to say that smaller elements on the periodic table, like No. 61, suddenly seemed passé. Uranium and plutonium and even heavier elements were where the real science was happening. In fact, the Oak Ridge team had discovered Element 61 only in its spare time, as a side venture during experiments on uranium.

The trio also gave its discovery an unsettling name, promethium. Prometheus was the Titan in Greek mythology who spurned the Olympian gods and gave the technology of fire to humankind. Humans didn't know how to use fire properly and it caused all sorts of destruction. The gods punished Prometheus by chaining him to a rock and letting a vulture eat his liver each day. (It grew back at night.)

Considering that promethium was useless, little more than a hole-plugger on the periodic table, it's hard to see what the Oak Ridge scientists were getting at with that name—unless they were really thinking of the potential fiery destruction that elements like uranium and plutonium could unleash. It was a signal that, after decades of filling in the middle ground of the periodic table, scientists had shifted their attention to the heavier and far more dangerous elements along the bottom row.

Sam Kean is the best-selling author of The Disappearing Spoon and The Violinist’s Thumb. His new book, The Tale of the Dueling Neurosurgeons, comes out May 6.