Lawrencium
Lawrencium (Unniltrium, Unt, eka-Lutetium) is a
radioactive synthetic element in the
periodic table that has the symbol
Lr and
atomic number 103. Its most stable isotope is
262Lr, with a
half-life of approximately 4
hours. Lawrencium is synthesized from
californium and has no known uses.
The appearance of this element is unknown, however it is most likely silvery-white or gray and
metallic. If sufficient amounts of lawrencium were produced, it would pose a
radiation hazard. Very little is known about the chemical properties of this element but some preliminary work on a few atoms has indicated that it behaves similarly to the
actinides.
Element 103 is a
d-block element analogous to
lutetium and therefore is increasingly being placed with the other d-block elements in the
transition metal chemical series, but it is still most often grouped with the
actinides in the periodic table.
Lawrencium was
discovered by
Albert Ghiorso,
Torbjørn Sikkeland,
Almon Larsh and
Robert M. Latimer on
February 14,
1961 at the Berkeley Radiation Laboratory (now called
Lawrence Berkeley National Laboratory) on the
University of California, Berkeley campus. It was produced by bombarding a 3
milligram target composed of three isotopes of
californium with
boron-10 and B-11 ions in the
Heavy Ion Linear Accelerator (HILAC).
The transmutation nuclei became electrically charged, recoiled with a
helium atmosphere and were collected on a thin
copper conveyor tape. This tape was then moved in order to place the collected atoms in front of a series of
solid-state detectors. The Berkeley team reported that the
isotope 257103 was detected in this manner and decayed by emitting an 8.6 MeV
alpha particle with a
half-life of 4.2 seconds.
In
1967, researchers in
Dubna,
Russia reported that they were not able to confirm an alpha emitter with a half-life of 4.2 seconds as
257103. This assignment has since been changed to
258Lr or
259Lr. Eleven isotopes of element 103 have been synthesized with
262Lr being the longest lived with a half-life of 216 minutes (it decays into
256No. The isotopes of lawrencium decay via
alpha emission,
spontaneous fission and
electron capture (in order of most to least common types).
The origin of the name, preferred by the
American Chemical Society, is in reference to
Ernest O. Lawrence, inventor of the
cyclotron. The symbol
Lw was originally used but in
1963 it was changed to
Lr. In August
1997 the
International Union of Pure and Applied Chemistry (IUPAC) ratified the name lawrencium and symbol
Lr during a meeting in
Geneva. Unniltrium was sometimes used as a temporary,
systematic element name until that time.
*
Los Alamos National Laboratory's Chemistry Division: Periodic Table - LawrenciumGuide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
*
WebElements.com - Lawrencium
