page_title: Lawrencium
section_title: History
hierarchical_section_title: Lawrencium / History
caption_attribution_description: English: Ernest O. Lawrence
context_page_description: Lawrencium is a synthetic chemical element with the symbol Lr and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radioactive metal, lawrencium is the eleventh transuranic element and is also the final member of the actinide series. Like all elements with atomic number over 100, lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles. Thirteen isotopes of lawrencium are currently known; the most stable is ²⁶⁶Lr with a half-life of 11 hours, but the shorter-lived ²⁶⁰Lr is most commonly used in chemistry because it can be produced on a larger scale.
  Chemistry experiments have confirmed that lawrencium behaves as a heavier homolog to lutetium in the periodic table, and is a trivalent element. It thus could also be classified as the first of the 7th-period transition metals: however, its electron configuration is anomalous for its position in the periodic table, having an s²p configuration instead of the s²d configuration of its homolog lutetium.
context_section_description: In 1958, scientists at the Lawrence Berkeley National Laboratory claimed the discovery of element 102, now called nobelium. At the same time, they also attempted to synthesize element 103 by bombarding the same curium target used with nitrogen-14 ions. A follow-up on this experiment was not performed, as the target was destroyed. Eighteen tracks were noted, with decay energy around 9±1 MeV and half-life around ​¹⁄₄ s; the Berkeley team noted that while the cause could be the production of an isotope of element 103, other possibilities could not be ruled out. While the data agrees reasonably with that later discovered for ²⁵⁷Lr (alpha decay energy 8.87 MeV, half-life 0.6 s), the evidence obtained in this experiment fell far short of the strength required to conclusively demonstrate the synthesis of element 103. Later, in 1960, the Lawrence Berkeley Laboratory attempted to synthesize the element by bombarding ²⁵²Cf with ¹⁰B and ¹¹B. The results of this experiment were not conclusive.
  The first important work on element 103 was carried out at Berkeley by the nuclear-physics team of Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh, Robert M. Latimer, and their co-workers on February 14, 1961. The first atoms of lawrencium were reportedly produced by bombarding a three-milligram target consisting of three isotopes of the element californium with boron-10 and boron-11 nuclei from the Heavy Ion Linear Accelerator (HILAC). The Berkeley team reported that the isotope ²⁵⁷103 was detected in this manner, and that it decayed by emitting an 8.6 MeV alpha particle with a half-life of 8±2 s. This identification was later corrected to be ²⁵⁸103, as later work proved that ²⁵⁷Lr did not have the properties detected, but ²⁵⁸Lr did. This was considered at the time to be convincing proof of the synthesis of element 103: while the mass assignment was less certain and proved to be mistaken, it did not affect the arguments in favor of element 103 having been synthesized. Scientists at the Joint Institute for Nuclear Research in Dubna (then in the Soviet Union) raised several criticisms: all but one were answered adequately. The exception was that ²⁵²Cf was the most common isotope in the target, and in the reactions with ¹⁰B, ²⁵⁸Lr could only have been produced by emitting four neutrons, and emitting three neutrons was expected to be much less likely than emitting four or five. This would lead to a narrow yield curve, not the broad one reported by the Berkeley team. A possible explanation was that there was a low number of events attributed to element 103. This was an important intermediate step to the unquestioned discovery of element 103, although the evidence was not completely convincing. The Berkeley team proposed the name "lawrencium" with symbol "Lw", after Ernest Lawrence, inventor of the cyclotron. The IUPAC Commission on Nomenclature of Inorganic Chemistry accepted the name, but changed the symbol to "Lr". This acceptance of the discovery was later characterized as being hasty by the Dubna team.
  ²⁵²
  ₉₈Cf
   + ¹¹
  ₅B
   → ²⁶³
  ₁₀₃Lr
  * → ²⁵⁸
  ₁₀₃Lr
   + 5 ¹
  ₀n
  The first work at Dubna on element 103 came in 1965, when they reported to have created ²⁵⁶103 in 1965 by bombarding ²⁴³Am with ¹⁸O, identifying it indirectly from its granddaughter fermium-252. The half-life they reported was somewhat too high, possibly due to background events. Later 1967 work on the same reaction identified two decay energies in the ranges 8.35–8.50 MeV and 8.50–8.60 MeV: these were assigned to ²⁵⁶103 and ²⁵⁷103. Despite repeated attempts, they were unable to confirm assignment of an alpha emitter with a half-life of eight seconds to ²⁵⁷103. The Russians proposed the name "rutherfordium" for the new element in 1967: this name was later used for element 104.
  ²⁴³
  ₉₅Am
   + ¹⁸
  ₈O
   → ²⁶¹
  ₁₀₃Lr
  * → ²⁵⁶
  ₁₀₃Lr
   + 5 ¹
  ₀n
  Further experiments in 1969 at Dubna and in 1970 at Berkeley demonstrated an actinide chemistry for the new element, so that by 1970 it was known that element 103 is the last actinide. In 1970, the Dubna group reported the synthesis of ²⁵⁵103 with half-life 20 s an
caption: The element was named after Ernest Lawrence.
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