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Lanthanum (La)

Lanthanum is a chemical element of the periodic table with chemical symbol La and atomic number 57 with an atomic weight of 138.905 u and is classed as lanthanide and is part of group 3 (scandium group). Lanthanum is solid at room temperature.

Lanthanum in the periodic table

Atomic number57
Group3 (Scandium group)
AppearanceSilvery white
Color Silver
Number of protons57 p+
Number of neutrons82 n0
Number of electrons57 e-
From Wikipedia, the free encyclopediaLanthanum is a soft, ductile, silvery-white metallic chemical element with symbol La and atomic number 57. It tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It gave its name to the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table:it is also sometimes considered the first element of the 6th-period transition metals.

Physical properties

Phase at STPSolid
Density6.162 g/cm3
Atomic weight138.905 u

Thermal properties

Melting point1193 K
919.85 °C
1687.73 °F
Boiling point3737 K
3463.85 °C
6266.93 °F
Heat of vaporization399.57 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)1.1
Electron affinity53 kJ/mol
Oxidation states0, +1, +2, +3
(a strongly basic oxide)
Ionization energies
  1. 538.1 kJ/mol
  2. 1067 kJ/mol
  3. 1850.3 kJ/mol
  4. 4819 kJ/mol
  5. 5940 kJ/mol

Electron configuration for lanthanum

Electron configuration
Shorthand configuration
[Xe] 5d1 6s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2
Electron configuration chart
Electrons per shell2, 8, 18, 18, 9, 2
Valence electrons 2
Valency electrons 3
Bohr model
LanthanumElectron shell for Lanthanum, created by Injosoft ABLa
Figure: Shell diagram of Lanthanum (La) atom.
Orbital Diagram

The history of Lanthanum

DiscoveryCarl Gustaf Mosander (1838)
Named byCarl Gustaf Mosander
Discovery of lanthanum
In 1751, the Swedish mineralogist Axel Fredrik Cronstedt discovered a heavy mineral from the mine at Bastnäs, later named cerite. Thirty years later, the fifteen-year-old Wilhelm Hisinger, from the family owning the mine, sent a sample of it to Carl Scheele, who did not find any new elements within. In 1803, after Hisinger had become an ironmaster, he returned to the mineral with Jöns Jacob Berzelius and isolated a new oxide which they named ceria after the dwarf planet Ceres, which had been discovered two years earlier. Ceria was simultaneously independently isolated in Germany by Martin Heinrich Klaproth. Between 1839 and 1843, ceria was shown to be a mixture of oxides by the Swedish surgeon and chemist Carl Gustaf Mosander, who lived in the same house as Berzelius and studied under him: he separated out two other oxides which he named lanthana and didymia. He partially decomposed a sample of cerium nitrate by roasting it in air and then treating the resulting oxide with dilute nitric acid. 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. Since lanthanum's properties differed only slightly from those of cerium, and occurred along with it in its salts, he named it from the Ancient Greek λανθάνειν [lanthanein] (lit. to lie hidden). Relatively pure lanthanum metal was first isolated in 1923.


List of unique identifiers for Lanthanum in various chemical registry databases
CAS Number7439-91-0
ChemSpider ID22369
EC number231-099-0
PubChem CID Number23926