Seaborgium

Sg Seaborgium

Proposed Name

History

In June 1974, members of the Joint Institute for Nuclear Research in Dubna, U.S.S.R., reported their discovery of Element 106, which they reported to have synthesized. Glenn Seaborg was part of this group, and the element was named in his honor. Seaborgium is often still referred to as Element 106 because the international committee in charge of names changed the rules. They decided retroactively it couldn't be named after a living person.

In September 1974, workers of the Lawrence Berkeley and Livermore Laboratories also claimed creation Element 106 "without any scientific doubt." The LBL and LLL Group used the Super HILAC to accelerate 18O ions onto a 249Cf target.

Element 106 was created by the reaction 249Cf(18O, 4N)263X, which decayed by alpha emission to rutherfordium, and then by alpha emission to nobelium, which in turn further decayed by

alpha between daughter and granddaughter. The element so identified had alpha energies of 9.06 and 9.25 MeV with a half-life of 0.9 +/- 0.2 s.

At Dubna, 280-MeV ions of 54Cr from the 310-cm cyclotron were used to strike targets of 206Pb, 207Pb, and 208Pb, in separate runs. Foils exposed to a rotating target disc were used to detect spontaneous fission activities. The foils were etched and examined microscopically to detect the number of fission tracks and the half-life of the fission activity.

Other experiments were made to aid in confirmation of the discovery. Neither the Dubna team nor the Berkeley-Livermore Group has proposed a name as of yet for element 106 (unnilhexium).

Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.

Last Updated: 12/19/97, CST Information Services Team

http://pearl1.lanl.gov/periodic/elements/106.html [3/6/2001 8:38:20 AM]

Nobelium

Nobelium

History

(Alfred Nobel, discoverer of dynamite) Nobelium was unambiguiously discovered and identified in April 1958 at Berkeley by A. Ghiorso, T. Sikkeland, J.R. Walton, and G.T. Seaborg, who used a new double-recoil technique. A heavy-ion linear accelerator (HILAC) was used to bombard a thin target of curium (95% 244Cm and 4.5% 246Cm) with 12C ions to produce 102No according to the 246Cm(12C, 4n) reaction.

In 1957 workers in the United States, Britain, and Sweden announced the discovery of an isotope of element 102 with a 10-minute half-life at 8.5 MeV, as a result of bombarding 244Cm with 13C nuclei. On the basis of this experiment, the name nobelium was assigned and accepted by the Commission on Atomic Weights of the International Union of Pure and Applied Chemistry.

The acceptance of the name was premature because both Russian and American efforts now completely rule out the possibility of any isotope of Element 102 having a half-life of 10 min in the vicinity of 8.5 MeV. Early work in 1957 on the search for this element, in Russia at the Kurchatov Institute, was marred by the assignment of 8.9 +/- 0.4 MeV alpha radiation with a half-life of 2 to 40 sec, which was too indefinite to support discovery claims.

Confirmatory experiments at Berkeley in 1966 have shown the existence of 254-102 with a 55-s half-life, 252-102 with a 2.3-s half-life, and 257-102 with a 23-s half-life.

Following tradition giving the right to name an element to the discoverer(s), the Berkeley group in 1967, suggested that the hastily given name nobelium along with the symbol No , be retained.

Isotopes

Ten isotopes are now recognized, one of which -- 255-102 -- has a half-life of 3 minutes.

Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.

http://pearl1.lanl.gov/periodic/elements/102.html (1 of 2) [3/6/2001 8:38:20 AM]

Nobelium

Last Updated: 12/19/97, CST Information Services Team

http://pearl1.lanl.gov/periodic/elements/102.html (2 of 2) [3/6/2001 8:38:20 AM]

Neilsborium

Bh Bohrium

Formally known as Ns Nielsbohrium

Proposed Name

History

In 1976 Soviet scientists at Dubna announced they had synthesized element 107 by bombarding 204Bi with heavy nuclei of 54Cr. Reports say that experiments in 1975 had allowed scientists "to glimpse" the new element for 2/1000 s. A rapidly rotating cylinder, coated with a thin layer of bismuth metal, was used as a target. This was bombarded by a stream of 54Cr ions fired tangentially.

The existence of element 107 was confirmed by a team of West German physicists at the Heavy Ion Research Laboratory at Darmstadt, who created and identified six nuclei of element 107.

Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.

Last Updated: 10/20/1999, CST Information Services Team

http://pearl1.lanl.gov/periodic/elements/107.html [3/6/2001 8:38:20 AM]