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Barium - Lanthanum - Cerium

Name, Symbol, NumberLanthanum, La, 57
Chemical series Lanthanides
Group, Period, Block3 , 6 , f
Density, Hardness 6146 kg/m3, 2.5
Appearance silvery white
Atomic Properties
Atomic weight 138.9055 amu
Atomic radius (calc.) 195 (n/a) pm
Covalent radius 169 pm
van der Waals radius n/a pm
Electron configuration [Xe]5d5d16s2
e- 's per energy level2, 8,18,18, 9, 2
Oxidation states (Oxide) 3 (strong base)
Crystal structure hexagonal
Physical Properties
State of matter solid (__)
Melting point 1193 K (1688 F)
Boiling point 3730 K (6255 F)
Molar volume 22.39 ×1010-3 m3/mol
Heat of vaporization 414 kJ/mol
Heat of fusion 6.2 kJ/mol
Vapor pressure 1.33E-07 Pa at 1193 K
Velocity of sound 2475 m/s at 293.15 K
Electronegativity 1.1 (Pauling scale)
Specific heat capacity 190 J/(kg*K)
Electrical conductivity 1.26 106/m ohm
Thermal conductivity 13.5 W/(m*K)
1st ionization potential 538.1 kJ/mol
2nd ionization potential 1067 kJ/mol
3rd ionization potential 1850.3 kJ/mol
4th ionization potential 4819 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
137La{syn.}60,000 years e capture0.600137Ba
138La0.09%1.05E11 yearse capture1.737138Ba
138La0.09%1.05E11 yearsβ-1.044138Ce
139La99.91%La is stable with 82 neutrons
SI units & STP are used except where noted.
Lanthanum is a chemical element in the periodic table that has the symbol La and atomic number 57.

Table of contents
1 Notable Characteristics
2 Applications
3 History
4 Biological Role
5 Occurrence
6 Compounds
7 Isotopes
8 Precautions
9 External Links

Notable Characteristics

Lanthanum is a silvery white metallic element belonging to group 3 of the periodic table and often considered to be one of the lanthanides. Found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly.


Uses of lanthanum:


Lanthanum was discovered in
1839 by C. G. Mosander, when he partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the resulting solution, he isolated a new rare earth he called lantana. Lanthanum was isolated in relatively pure form in 1923.

The word lanthanum comes from the Greek lanthanein, to lie hidden.

Biological Role

Lanthanum has no known biological role.

The element is not absorbed orally, and when injected its elimination is very slow. Lanthanum carbonate is being studied as a compound to absorb excess phosphate in cases of end-stage renal failure. Some rare-earth chlorides, such as lanthanum chloride (LaCl3), are known to have anticoagulant properties.


Monazite (Ce, La, Th, Nd, Y)PO4, and bastnasite (Ce, La, Y)CO3F, are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent respectively.



Naturally occurring lanthanum is composed of one stable and one radioactive isotope; 139-La, and 138-La with the stable isotope, 139-La, being the most abundant (99.91% natural abundance). 31 radioisotopes have been characterized with the most stable being 138-La with a half-life of 1.05E 11 years, and 137-La with a half-life of 60,000 years. All of the remaining radioactive isotopes have half-lifes that are less than 24 hours and the majority of these have half lifes that are less than 1 minute. This element also has 3 meta states.

The isotopes of lanthanum range in atomic weight from 120 amu (120-La) to 152 amu (152-La).


Lanthanum has a low to moderate level of toxicity, and should be handled with care. In animals, the injection of lanthanum solutions produces glycohemia, low blood pressure, degeneration of the spleen and hepatic alterations.

External Links