Bomb-Born Elements

Like children of a secret marriage, Elements 99 and 100 have been belatedly recognized. In a letter to the Physical Review, groups of scientists at the University of California, Argonne National Laboratory and Los Alamos Scientific Laboratory told how they separated the two new elements out of radioactive debris collected from Test Mike, the thermonuclear device exploded in the Pacific in November 1952.

The elements were formed when neutrons from the explosion hit atoms of uranium 238 and were captured by its nucleus. In the case of Element 99, the U-238 captured 15 neutrons and emitted seven beta particles (electrons). Each beta particle emitted meant that a captured neutron had changed into a proton. So the U-238, which had 92 protons and 146 neutrons, turned into Element 99 with 99 protons and 154 neutrons. To form Element 100 (100 protons and 155 neutrons), the U-238 captured 17 neutrons and lost eight beta particles. The scientists suggested that Element 99 be named einsteinium, after Albert Einstein, and Element 100 fermium, after Enrico Fermi.

Both elements were later created deliberately by "fattening" plutonium with neutrons in the Arco, Idaho materials-testing reactor (TIME, March 8, 1954). but the news of their earlier and more violent birth was not declassified until this week. Probable reason: no one was supposed to know that UJ-238, which can be made to fission in a thermonuclear ex plosion, was a factor in Test Mike.

Even heavier elements can probably be made by the neutron-fattening process or found in bomb debris. One of them has been: Element 101. But all of these atomic monstrosities will be short-lived. The forces that hold nuclei together do not seem to work well above the weight of uranium. The outsized atoms either fission (split) spontaneously or turn into lighter elements by radioactive decay.

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