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synthetic element | [History]
Canadian, and British physicist); Rf; at. wt. [261]; at. no. 104.
In 1964, workers of the Joint Nuclear Research Institute at
Dubna (Russia) bombarded plutonium with accelerated 113
to 115 MeV neon ions. By measuring fission tracks in a special
glass with a microscope, they detected an isotope that decays
by spontaneous fission. They suggested that this isotope,
which has a half-life of 0.3 ± 0.1 s, might be 104.
Element 104, the first transactinide element, is expected to
have chemical properties similar to those of hafnium. It would,
for example, form a relatively volatile compound with chlorine
(a tetrachloride). The Soviet scientists have performed experiments
aimed at chemical identification, and have attempted
to show that the 0.3-s activity is more volatile than that of the
relatively nonvolatile actinide trichlorides. This experiment
does not fulfill the test of chemically separating the new element
from all others, but it provides important evidence for evaluation. New data, reportedly issued by Soviet scientists,
have reduced the half-life of the isotope they worked with
from 0.3 to 0.15 s. The Dubna scientists suggest the name
kurchatovium and symbol Ku for Element 104, in honor of
Igor Vasilevich Kurchatov (1903–1960), late Head of Soviet
Nuclear Research. The Dubna Group also has proposed the
name dubnium for Element 104. In 1969, Ghiorso, Nurmia,
Harris, K. A. Y. Eskola, and P. I. Eskola of the University of
California at Berkeley reported they had positively identified
two, and possibly three, isotopes of Element 104. The group
also indicated that after repeated attempts so far they have
been unable to produce isotope 260104 reported by the Dubna
groups in 1964. The discoveries at Berkeley were made by
bombarding a target of 249Cf with 12C nuclei of 71 MeV, and 13C
nuclei of 69 MeV. The combination of 12C with 249Cf followed
by instant emission of four neutrons produced Element 257104.
This isotope has a half-life of 4 to 5 s, decaying by emitting an
alpha particle into 253No, with a half-life of 105 s. The same
reaction, except with the emission of three neutrons, was
thought to have produced 258104 with a half-life of about 1/100
s. Element 259104 is formed by the merging of a 13C nuclei with
249Cf, followed by emission of three neutrons. This isotope has
a half-life of 3 to 4 s, and decays by emitting an alpha particle
into 255No, which has a half-life of 185 s. Thousands of atoms
of 257104 and 259104 have been detected. The Berkeley group
believes its identification of 258104 was correct. Eleven isotopes
of Element 104 have now been identified. The Berkeley
group proposed the name rutherfordium (symbol Rf) for the
new element, in honor of Ernest Rutherford. This name was
formally adapted by IUPAC in August 1997. |
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