Lanthanum (La)

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.

Lanthanum in the periodic table

SymbolLa
Atomic number57
Group3
Period6
Blockd
Element categoryLanthanide

Physical properties

Phase at STPSolid
Density6.162 g/cm3
Atomic weight138.905 u
Melting point1193 K
919.85 °C
1687.73 °F
Boiling point3737 K
3463.85 °C
6266.93 °F

Atomära egenskaper

Electronegativity (Pauling Scale)1.1
Electron affinity53 kJ/mol
Ionization energies
1538.1 kJ/mol
2 1067 kJ/mol
3 1850.3 kJ/mol
4 4819 kJ/mol
5 5940 kJ/mol

Electron configuration

Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2
Electrons per shell2, 8, 18, 18, 9, 2

History

Discovered1838
Discovered byCarl Gustaf Mosander