Atomic number:57

Group numbers:3

Period:6

Electronic configuration:[Xe] 5d¹ 6s²

Formal oxidation number:+3

Electronegativities:1.1

Atomic radius / pm:187

Relative atomic mass:138.90547 ± 0.00007

 

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.

Density / g dm^-3:6145 (298 K)

Molar volume / cm³mol^-1:22.60 (298 K)

Electrical resistivity / μΩcm:57 (20 °C)

Thermal conductivity / W m^-1K^-1:13.5

Melting point / °C:918

Boiling point / °C:3464

Heat of fusion / kJ mol^-1:10.04

Heat of vaporization / kJ mol^-1:402.1

Heat of atomization / kJ mol^-1:431.29

1st ionization energy / kJ mol^-1:538.10

2nd ionization energy / kJ mol^-1:1067.14

3rd ionization energy / kJ mol^-1:1850.34

in the atmosphere / ppm:-

in the Earth's crust / ppm:16

in the oceans / ppm:0.0003