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La - Lanthanum

Lanthanum

 Lanthanum 
La
Atomic Number: 57
Atomic Weight: 138.9055
Element Type: Transition Metal
Crystal Structure: Hexagonal
Melting Point: 918.0°C = 1684.4°F = 1191.15 K
Boiling Point: 3464.0°C = 6267.2°F = 3737.15 K
Critical Temp: °C = °F = K
Atomic Radius: 2.74 Å (Å = Angstrom = 10-10 m)
Covalent Radius: 1.69 Å
Electronegativity: 1.1

History

(Greek lanthanein, to lie hidden) Mosander in 1839 extracted a new earth lanthana, fromimpure cerium nitrate and recognized the new element.

Lanthanum was isolated in relatively pure form in 1923. Iron exchange and solventextraction techniques have led to much easier isolation of the so-called"rare-earth" elements.


Sources

Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, andbastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs inpercentages up to 25 percent and 38 percent respectively. Misch metal, used in makinglighter flints, contains about 25 percent lanthanum.

The availability of lanthanum and other rare earths has improved greatly in recentyears. The metal can be produced by reducing the anhydrous fluoride with calcium .







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(1879-1955)





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