|Atomic Number:||104||Atomic Symbol:||Rf|
|Atomic Weight:||260||Electron Configuration:||2-8-18-32-10-2|
|Melting Point:||oC||Boiling Point:||oC|
|Description:||A man-made radioactive transition metal.|
HistoryIn 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
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.
IsotopesIn 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 emiting 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.