Symbol	La
Atomic number	57
Group	3 (Scandium group)
Period	6
Block	d
Classification	Lanthanide

Appearance	Silvery white
Color	Silver

Number of protons	57 p+
Number of neutrons	82 n0
Number of electrons	57 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.

Phase at STP	Solid
Density	6.162 g/cm3
Atomic weight	138.905 u

Melting point	1193 K 919.85 °C 1687.73 °F
Boiling point	3737 K 3463.85 °C 6266.93 °F
Heat of vaporization	399.57 kJ/mol

Electronegativity (Pauling Scale)	1.1
Electron affinity	53 kJ/mol
Oxidation states	0, +1, +2, +3 (a strongly basic oxide)
Ionization energies	538.1 kJ/mol 1067 kJ/mol 1850.3 kJ/mol 4819 kJ/mol 5940 kJ/mol

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	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2
Electrons per shell	2, 8, 18, 18, 9, 2
Valence electrons	2
Valency electrons	3
Bohr model	Figure: Shell diagram of Lanthanum (La) atom.
Orbital Diagram	1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p 5d 6s

Discovery	Carl Gustaf Mosander (1838)
Named by	Carl 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.

CAS Number	7439-91-0
ChemSpider ID	22369
EC number	231-099-0
PubChem CID Number	23926