Naturally occurring lanthanum (57La) is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). There are 38 radioisotopes that have been characterized, with the most stable being 138La, with a half-life of 1.02×1011 years; 137La, with a half-life of 60,000 years and 140La, with a half-life of 1.6781 days. The remaining radioactive isotopes have half-lives that are less than a day and the majority of these have half-lives that are less than 1 minute. This element also has 12 nuclear isomers, the longest-lived of which is 132mLa, with a half-life of 24.3 minutes.
|Main isotopes of lanthanum (57La)|
|Standard atomic weight Ar, standard(La)|
isotopic mass (u)
|range of natural|
|117mLa||151(12) keV||10(5) ms||(9/2+)|
|124mLa||100(100)# keV||21(4) s||low(+#)|
|125mLa||107.0(10) keV||390(40) ms||(3/2+)|
|126mLa||210(410) keV||20(20) s||(0−,1−,2−)|
|127mLa||14.8(12) keV||3.7(4) min||β+||127Ba||(3/2+)|
|128mLa||100(100)# keV||<1.4 min||IT||128La||(1+,2−)|
|129mLa||172.1(4) keV||560(50) ms||IT||129La||11/2−|
|131mLa||304.52(24) keV||170(10) µs||11/2−|
|132mLa||188.18(11) keV||24.3(5) min||IT (76%)||132La||6−|
|136mLa||255(9) keV||114(3) ms||IT||136La||(8)(−#)|
|138La[n 4]||57||81||137.907112(4)||1.02(1)×1011 y||β+ (66.4%)||138Ba||5+||9.0(1)×10−4|
|138mLa||72.57(3) keV||116(5) ns||(3)+|
|140La[n 5]||57||83||139.9094776(26)||1.6781(3) d||β−||140Ce||3−|
|146La||57||89||145.92579(8)||6.27(10) s||β− (99.99%)||146Ce||2−|
|β−, n (.007%)||145Ce|
|146mLa||130(130) keV||10.0(1) s||β−||146Ce||(6−)|
|147La||57||90||146.92824(5)||4.015(8) s||β− (99.96%)||147Ce||(5/2+)|
|β−, n (.04%)||146Ce|
|148La||57||91||147.93223(6)||1.26(8) s||β− (99.85%)||148Ce||(2−)|
|β−, n (.15%)||147Ce|
|149La||57||92||148.93473(34)#||1.05(3) s||β− (98.6%)||149Ce||5/2+#|
|β−, n (1.4%)||148Ce|
|150La||57||93||149.93877(43)#||510(30) ms||β− (97.3%)||150Ce||(3+)|
|β−, n (2.7%)||149Ce|
|151La||57||94||150.94172(43)#||300# ms [>300 ns]||β−||151Ce||5/2+#|
|152La||57||95||151.94625(43)#||200# ms [>300 ns]||β−||152Ce|
|153La||57||96||152.94962(64)#||150# ms [>300 ns]||β−||153Ce||5/2+#|
Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile and silvery-white metal that tarnishes when exposed to air, and it is soft enough to be cut with a knife. Cerium is the second element in the lanthanide series, and while it often shows the +3 oxidation state characteristic of the series, it also exceptionally has a stable +4 state that does not oxidize water. It is also considered one of the rare-earth elements. Cerium has no biological role and is not very toxic.
Despite always occurring in combination with the other rare-earth elements in minerals such as those of the monazite and bastnäsite groups, cerium is easy to extract from its ores, as it can be distinguished among the lanthanides by its unique ability to be oxidized to the +4 state. It is the most common of the lanthanides, followed by neodymium, lanthanum, and praseodymium. It is the 26th-most abundant element, making up 66 ppm of the Earth's crust, half as much as chlorine and five times as much as lead.
Cerium was the first of the lanthanides to be discovered, in Bastnäs, Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year. In 1839 Carl Gustaf Mosander became the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, cerium(IV) oxide is used to polish glass and is an important part of catalytic converters. Cerium metal is used in ferrocerium lighters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources.Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. It is also sometimes considered the first element of the 6th-period transition metals, which would put it in group 3, although lutetium is sometimes placed in this position instead. Lanthanum is traditionally counted among the rare earth elements. The usual oxidation state is +3. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.
Lanthanum usually occurs together with cerium and the other rare earth elements. Lanthanum was first found by the Swedish chemist Carl Gustav Mosander in 1839 as an impurity in cerium nitrate – hence the name lanthanum, from the Ancient Greek λανθάνειν (lanthanein), meaning "to lie hidden". Although it is classified as a rare earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as lead. In minerals such as monazite and bastnäsite, lanthanum composes about a quarter of the lanthanide content. It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923.
Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon arc lamps for studio lights and projectors, ignition elements in lighters and torches, electron cathodes, scintillators, GTAW electrodes, and other things. Lanthanum carbonate is used as a phosphate binder in cases of renal failure.