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Element Fact
Iridium is the most corrosion-resistant metal known. Together with platinum, it is used to make the international prototype of the kilogram, which is the standard definition for the unit of mass.

Lawrencium, Lr

lawrencium sample

Atomic number: 103
Atomic mass: [262] (no stable nuclide)
Natural abundance: -
Isotopes: -

History and Production

Named after E.O. Lawrence (1901-1958), inventor of the cyclotron. The atomic symbol Lr was adopted by IUPAC in 1965. Formerly it was Lw. The element was discovered by A. Ghiorso, T. Sikkeland, A.E. Larsch and R.M. Latimer in 1961, from bombardment of mixed isotopes of californium with 10B and 11B. They reported an isotope 257Lr with a half-life of 8 seconds was produced. Repeated experiments carried out elsewhere reassigned it to 258Lr or 259Lr. Ten isotopes are now discovered. 256Lr which has a half-life of 35 seconds was used in 1968 to study the oxidation behavior of the element at Berkeley. Obviously, the experiment was conducted very rapidly, involving solvent extraction techniques which took about 30 seconds to complete.

Physical Data

Its physical properties are not known since only atomic quantities have been produced so far which quickly dissappear when first prepared.

Interatomic distance: -
Melting point: n/a
Boiling point: n/a
Thermal conductivity/Wm-1K-1: 10 est. (27C)
Density/kgm-3: n/a

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: -
Gibbs free energy of formation: -
Entropy: -
Heat capacity: -

Electronic data

Electronic configuration: Electronic configuration: [Rn] 5f14 6d1 7s2
Term symbol: 2D5/2
Electron affinity: -   Electronegativity (Pauline): -
Ionization energy (first, second, third): 472.8, -, - kJ/mol

Chemical properties

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