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Lawrencium

Chemical element, symbol Lr and atomic number 103 / From Wikipedia, the free encyclopedia

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Lawrencium is a synthetic chemical element; it has symbol Lr (formerly Lw) 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 the last 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. Fourteen isotopes of lawrencium are currently known; the most stable is 266Lr with half-life 11 hours, but the shorter-lived 260Lr (half-life 2.7 minutes) is most commonly used in chemistry because it can be produced on a larger scale.

Quick facts: Lawrencium, Pronunciation, Appearance, Mass n...
Lawrencium, 103Lr
Lawrencium
Pronunciation/lɒˈrɛnsiəm/ (lo-REN-see-əm)
Appearancesilvery (predicted)[1]
Mass number[266]
Lawrencium in the periodic table
Lu

Lr

(Ups)
nobeliumlawrenciumrutherfordium
Atomic number (Z)103
Groupgroup 3
Periodperiod 7
Block  d-block
Electron configuration[Rn] 5f14 7s2 7p1
Electrons per shell2, 8, 18, 32, 32, 8, 3
Physical properties
Phase at STPsolid (predicted)
Melting point1900 K (1600 °C, 3000 °F) (predicted)
Density (near r.t.)14.4 g/cm3 (predicted)[2]
Atomic properties
Oxidation states+3
ElectronegativityPauling scale: 1.3 (predicted)[3]
Ionization energies
  • 1st: 479 kJ/mol[4]
  • 2nd: 1428.0 kJ/mol (predicted)
  • 3rd: 2219.1 kJ/mol (predicted)
Other properties
Natural occurrencesynthetic
Crystal structure hexagonal close-packed (hcp)
Hexagonal close-packed crystal structure for lawrencium

(predicted)[5]
CAS Number22537-19-5
History
Namingafter Ernest Lawrence
DiscoveryLawrence Berkeley National Laboratory and Joint Institute for Nuclear Research (1961–1971)
Isotopes of lawrencium
Main isotopes[6] Decay
abun­dance half-life (t1/2) mode pro­duct
256Lr synth 27.9 s α 252Md
β+ 256No
260Lr synth 3.0 min α 256Md
β+ 260No
261Lr synth 39 min SF
262Lr synth 4 h β+ 262No
264Lr synth 4.8 h[7] SF
266Lr synth 11 h SF
Symbol_category_class.svg Category: Lawrencium
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Chemistry experiments confirm 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. 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. However, this does not appear to affect lawrencium's chemistry.

In the 1950s, 1960s, and 1970s, many claims of the synthesis of lawrencium of varying quality were made from laboratories in the Soviet Union and the United States. The priority of the discovery and therefore the name of the element was disputed between Soviet and American scientists. The International Union of Pure and Applied Chemistry (IUPAC) initially established lawrencium as the official name for the element and gave the American team credit for the discovery; this was reevaluated in 1997, giving both teams shared credit for the discovery but not changing the element's name.

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