Rutherfordium
Atomic research: 104
Atomic Symbol: Rf / Ku
Atomic Weight: 261
Electron
Configuration: [Rn]7s²5f¹⁴6d²
History
In 1964, workers at the Joint Nuclear Research Institute at Dubna (U.S.S.R.)
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 had
a half-life of 0.3 +/- 0.1 s might be 260-104,
produced by the following reaction: 242Pu + 22Ne --> 104
+4n.
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), former Head of Soviet Nuclear Research.
Research
In 1969 Ghiorso, Nurmia, Harris, K.A.Y. Eskola, and P.L. Eskola of the
University of California at
Berkeley reported that they had positively
identified two, and possibly three, isotopes of Element 104.
The group
indicated that, after repeated attempts, they produced isotope 260-104
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 257-104. 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 258-104
with a
half-life of about 1/100 s.
Element 259-104 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 257-104 and 259-104 have ben detected. The Berkeley group believes
their
identification of 258-104 is correct, but attaches less
confidence to this work than to their work on
257-104 and 259-104.
The
claims for discovery and the naming of Element 104 are still in question.
The Berkeley group
proposes for the new element the name rutherfordium
(symbol Rf), in honor of Ernest R. Rutherford, a
New Zealand physicist.
Meanwhile, the International Union of Pure and Applied Physics has
proposed
using the neutral temporary name, unnilquadium.