Relative atomic mass: 138.90547 +- 0.00007

English: Lanthanum
French: Lanthane
Croatian: Lantan
German: Lanthan
Italian: Lantanio
Spanish: Lantano

Atomic number: 57
Group numbers: 3
Period: 6
Standard state (20 oC): solid

Discovery: 1839 Carl Gustaf Mosander (SE)
Lanthanum was discovered by Carl Gustaf Mosander (SE) in 1839. The origin of the name comes from the Greek word lanthanein meaning to lie hidden. It is a soft, silvery-white, malleable, ductile metal that tarnishes readily in air and reacts with oxidants. Reaction with water releases hydrogen gas, metal ignites and burns readily. Lanthanum is found with rare earths in monazite and bastnasite. Monazite sand typical contains 25% lanthanum. It is used in the electrodes of high-intensity, carbon-arc lights. Because it gives glass refractive properties, it is used in expensive camera lenses. The price of 99.9 % pure lanthanum pieces is 232.50 for 100 g.
Electronic configuration: [Xe] 5d1 6s2
Formal oxidation number: +3
Atomic radius: 187 pm

Electronegativities: 1.1
Thermal conductivity: 13.5 W/(m K)
Electrical resistivity (20 oC): 57 microOhm cm

Melting point: 918 oC
Boiling point: 3464 oC

Heat of fusion: 10.04 kJ/mol
Heat of vaporization: 402.1 kJ/mol
Heat of atomization: 431.29 kJ/mol

56Ba <= 57La => 58Ce

ASCII Periodic Table of the Elements
6 Jan. 2020
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