Lawrencium

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Lawrencium (IPA: /ləˈrɛnsiəm/) 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.

Notable characteristics

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 d-block, but it is an actinide according to IUPAC.

History

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 (IPA: /ˌjuːˈnɪltriəm/, symbol Unt) was sometimes used as a temporary, systematic element name until that time. Lawrencium has also been called eka-lutetium.

References

• 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

External links

• WebElements.com - Lawrencium