Discovery date : 1839
Discovered by: Carl Gustav Mosander
Origin of the name: The name is derived from the Greek 'lanthanein', meaning to lie hidden.
Allotropes :
~>LANTHANUM is a chemical element with symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife.
| FACT BOX | |||
| Group | Lanthanides | Melting point | 920°C, 1688°F, 1193 K |
| Period | 6 | Boiling point | 3464°C, 6267°F, 3737 K |
| Block | d | Density (g cm−3) | 6.15 |
| Atomic number | 57 | Relative atomic mass | 138.905 |
| State at 20°C | Solid | Key isotopes | 139La |
| Electron configuration | [Xe] 5d16 | CAS number | 7439-91-0 |
| ChemSpider ID | 22369 | ChemSpider is a free chemical structure database | |
Lanthanum was discovered in January 1839 by Carl Gustav Mosander at the Karolinska Institute, Stockholm. He extracted it from cerium which had been discovered in 1803. Mosander noticed that while most of his sample of cerium oxide was insoluble, some was soluble and he deduced that this was the oxide of a new element. News of his discovery spread, but Mosander was strangely silent.
That same year, Axel Erdmann, a student also at the Karolinska Institute, discovered lanthanum in a new mineral from Låven island located in a Norwegian fjord.
Finally, Mosander explained his delay, saying that he had extracted a second element from cerium, and this he called didymium. Although he didn’t realise it, didymium too was a mixture, and in 1885 it was separated into praseodymium and neodymium.