title="[95]Am[240] + α → [97]Bk[243] + [0]n[1]," tag="{http://www.w3.org/1999/xhtml}img"/>

and

The next two elements, einsteinium (₉₉Es) and fermium (₁₀₀Fm), were originally found in the debris from the thermonuclear device "Mike," which was detonated on Eniwetok atoll November 1952. (This method of creating new substances is somewhat more extravagant than the mythical Chinese method of burning down a building to get a roast pig.)

These elements have since been made in nuclear reactors and by bombardment. This time the "bullet" was N¹⁴ stripped of electrons till it had a charge of +6, and the target was plutonium.

Researchers at the University of California used new techniques in forming and identifying element 101, mendelevium. A very thin layer of ₉₉Es²⁵³ was electroplated onto a thin gold foil and was then bombarded, from behind the layer, with 41-MeV α particles. Unchanged ₉₉Es²⁵³ stayed on the gold, but those atoms hit by α particles were knocked off and deposited on a "catcher" gold foil, which was then dissolved and analyzed (Fig. 3). This freed the new element from most of the very reactive parent substances, so that analysis was easier. Even so, the radioactivity was so weak that the new element was identified "one atom at a time"; this is possible because its daughter element, fermium, spontaneously fissions and releases energy in greater bursts than any possible contaminant.

Fig. 3. The production of mendelevium.

In 1957, in Stockholm, element 102 was reported found by an international team of scientists (who called it nobelium), but diligent and extensive research failed to duplicate the Stockholm findings. However, a still newer technique developed at Berkeley showed the footprints—if not the living presence—of 102 (see Fig. 4). The rare isotope curium-246 is coated on a small piece of nickel foil, enclosed in a helium-filled container, and placed in the heavy-ion linear accelerator (Hilac) beam. Positively charged atoms of element 102 are knocked off the foil by the beam, which is of carbon-12 or carbon-13 nuclei, and are deposited on a negatively charged conveyor apron. But element 102 doesn't live long enough to be actually measured. As it decays, its daughter product, ₁₀₀Fm²⁵⁰, is attracted onto a charged aluminum foil where it can be analyzed. The researchers have decided that the hen really did come first: they have the egg; therefore the hen must have existed. By measuring the time distance between target and daughter product, they figure that the hen-mother (element 102) must have a half-life of three seconds.

Fig. 4. The experimental arrangement used in the discovery of element 102.

In an experiment completed in 1961, researchers at the University of California at Berkeley unearthed similar "footprints" belonging to element 103 (named lawrencium in honor of Nobel prizewinner Ernest O. Lawrence). They found that the bombardment of californium with boron ions