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Lawrencium


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Atomic Number:103Atomic Symbol:Lr
Atomic Weight:262Electron Configuration:2-8-18-32-32-9-2
Shells:2,8,18,32,32,9,2Filling Orbital:5f14
Melting Point:oCBoiling Point:oC
Description:Man made radioactive metal.

History

(Ernest O. Lawrence, inventor of the cyclotron)
  • This member of the 5f transition elements (actinide series) was discovered in March 1961 by A. Ghiorso, T. Sikkeland, A.E. Larsh, and R.M. Latimer.
  • A 3-Mg californium target, consisting of a mixture of isotopes of mass number 249, 250, 251, and 252, was bombarded with either 10B or 11B.
  • The electrically charged transmutation nuclei recoiled with an atmosphere of helium and were collected on a thin copper conveyor tape which was then moved to place collected atoms in front of a series of solid-state detectors.
  • The isotope of element 103 produced in this way decayed by emitting an 8.6 MeV alpha particle with a half-life of 8 s.
  • In 1967, Flerov and associates at the Dubna Laboratory reported their inability to detect an alpha emitter with a half-life of 8 s which was assigned by the Berkeley group to 257-103.
  • This assignment has been changed to 258Lr or 259Lr.
  • In 1965, the Dubna workers found a longer-lived lawrencium isotope, 256Lr, with a half-life of 35 s.
  • In 1968, Thiorso and associates at Berkeley used a few atoms of this isotope to study the oxidation behavior of lawrencium.
  • Using solvent extraction techniques and working very rapidly, they extracted lawrencium ions from a buffered aqueous solution into an organic solvent -- completing each extraction in about 30 s.

Properties

Lawrencium behaves differently from dipositive nobelium and more like the tripositive elements earlier in the actinide series.

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