|Name, Symbol, Number||lawrencium, Lr, 103|
|Group, Period, Block||n/a, 7, d|
|Appearance||unknown, probably silvery|
white or metallic gray
|Standard atomic weight||(262) g·mol−1|
|Electron configuration||[Rn] 5f14 6d1 7s2|
|Electrons per shell||2, 8, 18, 32, 32, 8, 3|
|Phase||presumably a solid|
|Melting point||1900 K|
(1627 °C, 2961 °F)
|Electronegativity||1.3 (scale Pauling)|
|Ionization energies||1st: 470 kJ/mol|
|CAS registry number||22537-19-5|
Lawrencium (pronounced /ləˈrɛnsiəm/) is a radioactive synthetic element with the symbol Lr (formerly Lw) 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 other actinides.
A strict correlation between periodic table blocks and chemical series for neutral atoms would describe lawrencium as a transition metal because it is in the F-block, but it is an actinide according to IUPAC.
Lawrencium was discovered by Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, and Robert M. Latimer on February 14, 1961 at the Lawrence Radiation Laboratory (now called Lawrence Berkeley National Laboratory) on the University of California, Berkeley campus. It was produced by bombarding a three 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. 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 originally was 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 (IPA: /juːˈnɪltriəm/, symbol Unt) was sometimes used as a temporary, systematic element name until that time. Lawrencium also has been called eka-lutetium.
- IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the "Red Book" IR 3-6)
- Glenn T. Seaborg (1951-12-12). "The transuranium elements: present status (Nobel Lecture)" (PDF).
- Los Alamos National Laboratory's Chemistry Division: Periodic Table - Lawrencium
- Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
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