Lanthanum is a chemical element with the symbol La and atomic number 57.
Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is a lanthanide. Found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly.
Technical Data
Symbol |
La |
Density (20°C)/gcm3 |
6.17 |
Atomic number |
57 |
Melting point / °C |
920 |
No. of naturally occurring isotopes |
2 |
Boiling point / °C |
3420 |
Atomic weight |
138.9055 |
ΔHfus/kJmol-1 |
8.5 |
Electronic configuration |
[Xe]5d16s2 |
ΔHvap/kJmol-1 |
402 |
Metal radius( 12-coordinate)/pm |
187 |
ΔHf(monoatomic gas/kJmol-1 |
423(+/-6) |
Ionic radius(6-coordinate)/pm |
103.2 |
Electronegativity χ |
1.1 |
Ionization energy Idmol-1 I |
538 |
Electrical resistisvity |
|
Ionization energy/kJmol-1 II |
1067 |
(20°C)/μohm cm |
57-80 |
Ionization energy/kJmol-1 III |
1850 |
Eo(M3+(aq)+ 3e- →M(S))/V |
-2.522 |
Evaporation Techniques
Temperature (oC) @Vap. Pressure |
Techniques |
Remarks |
10-8 Torr |
10-6 Torr |
10-4 Torr |
Electron Beam |
Crucible |
Coil |
Boat |
990 |
1212 |
1388 |
Excellent |
Al2O3 |
- |
Tungsten & Tantalum |
Films will burn in air if scraped |
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