Lanthanum

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Lanthanum,  57La
General properties
Name, symbol Lanthanum, La
Appearance Silvery-white
Lanthanum in the periodic table
Y

La

Ac
BariumLanthanumCerium
Atomic number 57
Standard atomic weight (Ar) 138.90547(7)
Group, block , d-block
Period period 6
Electron configuration [Xe] 5d1 6s2
Physical properties
Silvery-white
Phase Solid
Melting point 1193 K ​(920 °C, ​1688 °F)
Boiling point 3737 K ​(3464 °C, ​​6267 °F)
Density near r.t. 6.162 g/cm3
when liquid, at  5.94 g/cm3
Heat of fusion 6.20 kJ/mol
Heat of 400 kJ/mol
Molar heat capacity 27.11 J/(mol·K)
 pressure
Atomic properties
Oxidation states 3, 2, 1 ​(a strongly basic oxide)
Electronegativity Pauling scale: 1.10
energies 1st: 538.1 kJ/mol
2nd: 1067 kJ/mol
3rd: 1850.3 kJ/mol
Atomic radius empirical: 187 pm
Covalent radius 207±8 pm
Miscellanea
Crystal structure ​Double hexagonal close-packed (dhcp)
Speed of sound thin rod 2475 m/s (at 20 °C)
Thermal expansion 12.1 µm/(m·K) (α, poly)
Thermal conductivity 13.4 W/(m·K)
Electrical resistivity 6.15·10-7 Ω·m (α, poly)
Magnetic ordering Paramagnetic
Young's modulus 36.6 GPa (α, poly)
Shear modulus 14.3 GPa (α, poly)
Bulk modulus 27.9 GPa (α, poly)
Poisson ratio 0.28 (α, poly)
Mohs hardness 2.5
Vickers hardness 360–1750 MPa
Brinell hardness 350–400 MPa
CAS Registry Number 7439-91-0
History
Discovery Carl Gustaf Mosander (1838)
· references

Lanthanum is a rare-earth metal with chemical symbol La, and an atomic weight of 57. Lanthanum is the first element in the lanthanide series.

Lanthanum's position in the periodic table is shown different depending on the type of table. Some models put it in group 3, others or at the end of the f block with lutetium and lawrencium instead, while other types of tables only have scandium and yttrium, leaving lanthanum in the f block.

Properties

Chemical

Lanthanum is one of the more reactive rare earth metals. It reacts slowly with cold water, and very quickly with hot water. It will also react with elemental halogens, chalcogens, as well as carbon, phosphorus, nitrogen, silicon, and boron.

Physical

Lanthanum is a silvery white metal that tarnishes quickly in contact with air. It is a very soft metal and can be cut with a knife.

Availability

Lanthanum is readily available from source such as Metallium and eBay.

Preparation

It is difficult to prepare lanthanum metal in an amateur setting, though a method for making rare earth metals, involving reducing the fluoride with calcium metal, is being developed by the Sciencemadness community.

Projects

  • Make Mischmetal
  • Nickel-metal hydride battery

Handling

Safety

Lanthanum metal will react with water to produce hydrogen, which is flammable. Lanthanum compounds are thought to be non-toxic, however not much research has been done on the toxicity so they should be handled with care.

Storage

Best stored under inert atmosphere.

Disposal

Best to try to recycle it.

References

Relevant Sciencemadness threads