Chapter 2

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, {100}Fm<250>, 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.

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 released [alpha] particles which had an energy of 8.6 MeV and decayed with a half-life of 8 ± 2 seconds. These particles can only be produced by element 103, which, according to one scientific theory, is a type of "dinosaur" of matter that died out a few weeks after creation of the universe.

The half-life of lawrencium (Lw) is about 8 seconds, and its mass number is thought to be 257, although further research is required to establish this conclusively.

Research on lawrencium is complicated. Its total [alpha] activity amounts to barely a few counts per hour. And, since scientists had the [alpha]-particle "footprints" only and not the beast itself, the complications increased. Therefore no direct chemical techniques could be used, and element 103 was the first to be discovered solely by nuclear methods.[A]

For many years the periodic system was considered closed at 92. It has now been extended by at least eleven places (Table I), and one of the extensions (plutonium) has been made in truckload lots. Its production and use affect the life of everyone in the United States and most of the world.

Surely the end is again in sight, at least for ordinary matter, although persistent scientists may shift their search to the other-world "anti" particles. These, too, will call for very special techniques for detection of their fleeting presence.

Early enthusiastic researchers complained that a man's life was not long enough to let him do all the work he would like on an element. The situation has now reached a state of equilibrium; neither man nor element lives long enough to permit all the desired work.

[A] In August 1964 Russian scientists claimed that they created element 104 with a half-life of about 0.3 seconds by bombarding plutomium with accelerated neon-22 ions.

Table I. THE TRANSURANIUM ELEMENTS

======================================================================== Element Name (Symbol) Mass Year Discovered; by whom; Number where; how ------------------------------------------------------------------------ 93 Neptunium (Np) 238 1940; E. M. McMillan, P. H. Abelson; University of California at Berkeley; slow-neutron bombardment of U<238> in the 60-inch cyclotron. ------------------------------------------------------------------------ 94 Plutonium (Pu) 238 1941; J. W. Kennedy, E. M. McMillan, G. T. Seaborg, and A. C. Wahl; University of California at Berkeley; 16-MeV deuteron bombardment of U<238> in the 60-inch cyclotron.

(Pu) 239 Pu<239>; the fissionable isotope of plutonium, was also discovered in 1941 by J. W. Kennedy, G. T. Seaborg, E. Segrè and A. C. Wahl; University of California at Berkeley; slow-neutron bombardment of U<238> in the 60-inch cyclotron. ------------------------------------------------------------------------ 95 Americium (Am) 241 1944-45; Berkeley scientists A. Ghiorso, R. A. James, L. O. Morgan, and G. T. Seaborg at the University of Chicago; intense neutron bombardment of plutonium in nuclear reactors. ------------------------------------------------------------------------ 96 Curium (Cm) 242 1945; Berkeley scientists A. Ghiorso, R. A. James, and G. T. Seaborg at the University of Chicago; bombardment of Pu<239> by 32-MeV helium ions from the 60-inch cyclotron. ------------------------------------------------------------------------ 97 Berkelium (Bk) 243 1949; S. G. Thompson, A. Ghiorso, and G. T. Seaborg; University of California at Berkeley; 35-MeV helium-ion bombardment of Am<241>. ------------------------------------------------------------------------ 98 Californium (Cf) 245 1950; S. G. Thompson, K. Street, A. Ghiorso, G. T. Seaborg; University of California at Berkeley; 35-MeV helium-ion bombardment of Cm<242>. ------------------------------------------------------------------------ 99 Einsteinium (Es) 253 1952-53; A. Ghiorso, S. G. 100 Fermium (Fm) 255 Thompson, G. H. Higgins, G. T. Seaborg, M. H. Studier, P. R. Fields, S. M. Fried, H. Diamond, J. F. Mech, G. L. Pyle, J. R. Huizenga, A. Hirsch, W. M. Manning, C. I. Browne, H. L. Smith, R. W. Spence; "Mike" explosion in South Pacific; work done at University of California at Berkeley, Los Alamos Scientific Laboratory, and Argonne National Laboratory; both elements created by multiple capture of neutrons in uranium of first detonation of a thermonuclear device. The elements were chemically isolated from the debris of the explosion. ------------------------------------------------------------------------ 101 Mendelevium (Md) 256 1955; A. Ghiorso, B. G. Harvey, G. R. Choppin, S. G. Thompson, G. T. Seaborg; University of California at Berkeley; 41-MeV helium-ion bombardment of Es<253> in 60-inch cyclotron. ------------------------------------------------------------------------ 102 Unnamed[B] 254 1958; A. Ghiorso, T. Sikkeland, A. E. Larsh, R. M. Latimer; University of California, Lawrence Radiation Laboratory, Berkeley; 68-MeV carbon-ion bombardment of Cm<246> in heavy-ion linear accelerator (Hilac). ------------------------------------------------------------------------ 103 Lawrencium 257 1961; A. Ghiorso, T. Sikkeland, A. E. Larsh, R. M. Latimer; University of California, Lawrence Radiation Laboratory, Berkeley; 70-MeV boron-ion bombardment of Cf<250>, Cf<251>, and Cf<252> in Hilac. ========================================================================

[B] A 1957 claim for the synthesis and identification of element 102 was accepted at that time by the International Union of Pure and Applied Chemistry, and the name nobelium (symbol No) was adopted. The University of California scientists, A. Ghiorso et al., cited here believe they have disproved the earlier claim and have the right to suggest a different name for the element.