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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.

Neodymium, Nd

neodymium sample

Atomic number: 60
Atomic mass: 144.24(3)
Natural abundance: 40 ppm
142Nd (141.907719) - 27.13%
143Nd (142.909810) - 12.18%
144Nd (143.910083) - 23.80%
145Nd (144.912569) - 8.30%
146Nd (145.913112) - 17.19%
148Nd (147.916889) - 5.76%
150Nd (149.920887) - 5.64%

History and Production

From Greek neos and didymod, meaning new twin. The impure oxide was first prepared from cerite by C.G. Mosander in 1841. He named the mixture didymium. It was until 1885 that C.A. von Welsbach separated the metal, along with praseodymium, from the mixture by repeated crystallization processes. Neodymium salts can be recovered from monazite and bastnaesite by using ion-exchange and solvent extraction techniques. The metal is subsequently obtained from the fluoride (NdF3) by reduction with calcium metal. It is used in misch metal alloy (about 18% Nd) for cigarette-lighter flints. In ceramic industry it is used for glazes and to color glass. It is also used in making laser material and protective goggles for glassblowers and welders. With iron and boron, it is used to make very strong magnets.

Physical Data

It is bright silvery-white, easily tarnishes in air forming a loose oxide film. It is therefore best kept sealed or under mineral oil. The metal exists in two allotropic forms, which changes from a double hexagonal structure to a body-centered cubic structure at around 863C. Its natural abundance is about 40 ppm and is usually associate with other rare earth metals in monazite sands, bastnaesite, cerite and orthite.

Interatomic distance: 362.8 pm
Melting point: 1021C
Boiling point: 3074C
Thermal conductivity/Wm-1K-1: 16.5 (27C)
Density/kgm-3: 7007 (20C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 327.6 kJ/mol
Gibbs free energy of formation: 292.4 kJ/mol
Entropy: 189.4 J/mol K
Heat capacity: 22.1 J/mol K

Electronic data

Electronic configuration: [Xe] 4f4 6s2
Term symbol: 5I4
Electron affinity: -   Electronegativity (Pauline): 1.14
Ionization energy (first, second, third): 533.082, 1035.29, 2132.33 kJ/mol

Chemical properties

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