By Ron B. Davis Jr., Georgetown University
As cyclotron and synchrotron technology progressed in the 1950s, newer and better designs were allowing scientists to use larger and larger ions as bombardment projectiles in the quest for heavier elements. Scientists turned to the periodic table as a recipe book for heavy element synthesis. This opened the remainder of row 7 of the periodic table to exploration.
The Hydrogen Bomb
In the years after the Manhattan project, the US government’s interest in superweapons continued, and in 1952 a new type of weapon was detonated—a hydrogen bomb. The hydrogen bomb uses the fusion of hydrogen to helium as its main payload. But getting the fusion reaction started requires temperatures and pressures that can only be generated by a fission device. That is, a first-generation fission nuclear bomb was needed to trigger the second-generation fusion nuclear bomb.
On November 1, 1952, the first ever thermonuclear device, codenamed Ivy Mike, was detonated in the Pacific Proving Grounds, in the Marshall Islands. The explosion created a fireball 5 kilometers wide. The estimated temperature within the fireball reached 150 million degrees centigrade, and the pressure climbed to 73 million atmospheres. The unimaginably high pressure and temperature, along with a neutron flux that could never be generated in a lab, transmuted some of the heavy elements from the fission stage into never-before seen elements.
Glen T. Seaborg’s Attempt
Samples of soil and air from the area surrounding the blast were taken to labs near Los Alamos and Chicago for analysis. Glen T. Seaborg, a Manhattan Project physicist, was no longer working for the US government, but he was by then a Nobel laureate with a proven track record of elemental discovery. After pulling some strings, Seaborg got his hands on some samples from the blast, and in short order elements 99 and 100 were discovered.
Under the unprecedented conditions of the Ivy Mike explosion, it appeared that a few atoms of uranium-238 absorbed a staggering 15 neutrons each, resulting in 7 beta decays, or 17 neutrons absorbed followed by eight beta decays.
This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.
Elements 99 and 100 of the Periodic Table
Unlike the discoveries of Berkelium and Californium, however, Seaborg couldn’t rush to press with his discovery and secure naming rights to the two elements because any scientific results related to the fusion-bomb project were classified by the US government.
In the months after the discovery, tensions grew between the Berkeley and Argonne labs. Many at Argonne felt that their contribution to the discovery of elements 99 and 100 were overlooked. Ultimately, Berkeley prevailed and was recognized as the discoverers of elements 99 and 100 of the periodic table.
And to the victor went the spoils—Seaborg’s team named them einsteinium and fermium. Albert Einstein and Enrico Fermi were not only two of the most revered physicists of the 20th century, Albert Einstein and Enrico Fermi, both prominent physicists, and perhaps ironically or maybe on purpose, both vocally opposed to the production of the hydrogen bomb itself.
Using Neutron Bombardment to Produce Elements 99 and 100
But using nuclear bombs to synthesize elements 99 and 100 was a less than ideal method, and as soon as it was known that these elements could be created at all, an effort was launched to produce them in a lab.
Formation of these elements by neutron capture would prove highly difficult, though not impossible. Some heavier isotopes of einsteinium have been generated by successive rounds of neutron bombardment of plutonium and uranium.
Although the results of thermonuclear testing showed that neutron bombardment can be used to produce elements 99 and 100, the tremendous number of neutrons that must be captured by the target nucleus led to diminishing returns in these larger nuclei, even in the lab.
The Swedish Experiment
In 1954, after Seaborg’s classified discovery of element 100 of the periodic table, but before their ability to publish their classified work, another group joined the race to discover new elements.
In Sweden, work began at the Nobel Institute for Physics—not to be confused with a Prize Committee that awards Nobel Prizes. They were using state-of-the-art cyclotrons to accelerate the nuclei of ever-larger elements to speeds that made it possible to overcome the coulombic barrier. Scientists at the Nobel Institute were able to fire oxygen ions at uranium, thereby directly adding the eight protons needed to leapfrog from element 92 to element 100 of the periodic table.
The Swedish experiment was published just days before Seaborg and Albert Ghiorso’s extended team of collaborators at Berkeley, Los Alamos, and Chicago produced element 100 by neutron bombardment.
Nobelium vs. Fermium
This race to discovery was no longer pitting just American academic and governmental labs against one another. A new international competition began to break out for the prestige of discovery and the rights to name new element, forever altering the most iconic scientific image ever—the periodic table.
But unaware of the classified American work that had taken place, the Nobel Institute scientists jumped to recommend their namesake with ‘nobelium’. But Ghiorso and Seaborg were careful to mention in their final published work on fermium that their group had, in fact, years earlier detected and isolated the fermium-255 while doing classified government work. This claim, and their reputation as heavyweights in element discovery is likely the reason why the scientific community quickly gave the nod to their name, ‘fermium’.
Interestingly, the fragmentation of the Manhattan project into academic and government enterprises, as well as the arrival of the Swedish Nobel Institute on the scene had caused more than a bit of controversy and competition to evolve around the periodic table’s heavy-element discovery.
Common Questions about the Race to Expand the Periodic Table
The unimaginably high pressure and temperature, along with a neutron flux that could never be generated in a lab, transmuted some of the heavy elements from the fission stage into never-before seen elements.
Glen T. Seaborg couldn’t rush to press with his discovery and secure naming rights to the two elements because any scientific results related to the fusion-bomb project were classified by the US government.
Albert Ghiorso and Glen T. Seaborg’s reputation as heavyweights in element discovery is likely the reason why the scientific community quickly gave the nod to their name, ‘fermium’.
