|Name, Symbol, Number||lawrencium, Lr, 103|
|Group, Period, Block||n/a, 7, d|
|Appearance||unknown, probably silvery
white or metallic gray
|Atomic mass||(262) g/mol|
|Electron configuration||probably [Rn] 5f14 7s2 6d1|
|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 (Pauling scale)|
|Ionization energies||1st: 470 kJ/mol|
|CAS registry number||22537-19-5|
Lawrencium (chemical symbol Lr, atomic number 103), once known as eka-lutetium, is a radioactive synthetic element in the periodic table. Its most stable isotope is 262Lr, with a half-life of approximately four hours. It is synthesized from californium and is of interest mainly for research purposes. It has no practical applications at this time.
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.
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 three milligram target composed of three isotopes of californium with boron-10 and boron-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).
If one were to follow a strict correlation between periodic table blocks and chemical series for neutral atoms, lawrencium would be described as a transition metal because it is in the d-block. The International Union of Pure and Applied Chemistry (IUPAC), however, recommends that it be classified as an actinide.
The appearance of this element is unknown, but it is likely to be 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 in a manner similar to other actinides.
All links retrieved July 26, 2014.
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