Science Fair Project Encyclopedia
|Name, Symbol, Number||lawrencium, Lr, 103|
|Chemical series||Transition metals|
|Group, Period, Block||3, 7, d|
|Appearance||unknown; probably metallic,|
silvery white or gray
|Atomic weight||[ 262 ] amu|
|Electron configuration||probably [Rn]5f14 6d1 7s2|
|e- 's per energy level||2, 8, 18, 32, 32, 9, 2|
|State of matter||presumably a solid|
Lawrencium is a synthetic element in the periodic table that has the symbol Lr and atomic number 103. A short-lived radioactive transuranic rare earth element, 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.
Lawrencium was, and often still is, grouped with the actinide chemical series in the periodic table. However, unlike all other rare earths, element 103 is a d-block element and therefore is increasingly being placed with the other d-block elements in the transition metal chemical series.
Lawrencium was discovered by Albert Ghiorso, Torbjorn 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 103-257 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 103-257. This assignment has since been changed to Lr-258 or Lr-259. Eleven isotopes of element 103 have been synthesized with Lr-262 being the longest lived with a half-life of 216 minutes (it decays into nobelium-256). 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.
- 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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