Lawrencium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

103 nobelium ← lawrencium → rutherfordium Lu ↑ Lr ↓ (Upt) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	lawrencium, Lr, 103
Chemical series	Transition metals
Group, Period, Block	3, 7, d
Appearance	unknown, probably silvery white or metallic gray
Atomic mass	(262) g/mol
Electron configuration	probably [Rn] 5f14 7s2 7p1
Electrons per shell	2, 8, 18, 32, 32, 8, 3
Phase	presumably a solid
Melting point	1900  K (1627 ° C, 2961 ° F)
Ionization energies	1st: 470 kJ/mol
CAS registry number	22537-19-5
References

Lawrencium ( IPA: /ləˈrɛnsiəm/), also called 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.

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 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 sometimes grouped with the actinides in the periodic table.

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.