Lanthanum

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Animated Lanthanum

History

From the Greek word lanthanein, to escape notice. Mosander in 1839 extracted lanthana from impure cerium nitrate and recognized the new element.

Lanthanum was isolated in relatively pure form in 1923. Iron exchange and solvent extraction techniques have led to much easier isolation of the so-called "rare-earth" elements.

Sources

Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent respectively. Misch metal, used in making lighter flints, contains about 25 percent lanthanum.

The availability of lanthanum and other rare earths has improved greatly in recent years. The metal can be produced by reducing the anhydrous fluoride with calcium.

Uses

Rare-earth compounds containing lanthanum are extensively used in carbon lighting applications, especially by the motion picture industry for studio lighting and projection. This application consumes about 25 percent of the rare-earth compounds produced. La2O3 improves the alkali resistance of glass, and is used in making special optical glasses. Small amounts of lanthanum, as an additive, can be used to produce nodular cast iron.

There is current interest in hydrogen sponge alloys containing lanthanum. These alloys take up to 400 times their own volume of hydrogen gas, and the process is reversible. Every time they take up the gas, heat energy is released; therefore these alloys have possibilities in an energy conservation system.

Isotopes

Natural lanthanum is a mixture of two stable isotopes, 138La and 139La. Twenty three other radioactive isotopes are recognized.

General Info

AtomicNumber
57
Symbol
La
Name
Lanthanum

Atomic Info

Appearance
AtomicWeight
138.90547(7)
Color
70D4FF
ElectronicConfiguration
[Xe] 5d1 6s2
ElectronegativityInPauling
1.1
AtomicRadiusInPM
169
IonRadiusInPM
103.2 (+3)
VanDerWaalsRadiusInPM
IEinKJmol
538
EAinKJmol
-48
OxidationStates
2, 3
StandardState
solid
BondingType
metallic
MeltingPoint
1193
BoilingPoint
3737
Density
6.15
State
Lanthanide
DiscoveredYear
1839