Lanthanum

Lanthanum,  ₅₇La

General properties
Name, symbol	Lanthanum, La
Appearance	Silvery-white
Lanthanum in the periodic table
Y ↑ La ↓ Ac Barium ← Lanthanum → Cerium
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)

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

• http://www.webelements.com/lanthanum/

Relevant Sciencemadness threads

• Lanthanum from pool cleaner
• How to store Lanthanum metal