Naturally occurring

lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between l ...

(₅₇La) is composed of one stable (¹³⁹La) and one

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

(¹³⁸La)

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...

, with the stable isotope, ¹³⁹La, being the most abundant (99.91% natural abundance). There are 38

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s that have been characterized, with the most stable being ¹³⁸La, with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

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 isomer A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...

s, the longest-lived of which is ^132mLa, with a half-life of 24.3 minutes. The isotopes of lanthanum range in

atomic weight Relative atomic mass (symbol: ''A''; sometimes abbreviated RAM or r.a.m.), also known by the deprecated synonym atomic weight, is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a giv ...

from 116.95 u (¹¹⁷La) to 154.96 u (¹⁵⁵La).

List of isotopes

, - , rowspan=2, ¹¹⁷La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 60 , rowspan=2, 116.95007(43)# , rowspan=2, 23.5(26) ms , β⁺ , ¹¹⁷Ba , rowspan=2, (3/2+, 3/2−) , rowspan=2, , rowspan=2, , - , p , ¹¹⁶Ba , - , style="text-indent:1em" , ^117mLa , colspan="3" style="text-indent:2em" , 151(12) keV , 10(5) ms , , , (9/2+) , , , - , ¹¹⁸La , style="text-align:right" , 57 , style="text-align:right" , 61 , 117.94673(32)# , 200# ms , β⁺ , ¹¹⁸Ba , , , , - , ¹¹⁹La , style="text-align:right" , 57 , style="text-align:right" , 62 , 118.94099(43)# , 1# s , β⁺ , ¹¹⁹Ba , 11/2−# , , , - , rowspan=2, ¹²⁰La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 63 , rowspan=2, 119.93807(54)# , rowspan=2, 2.8(2) s , β⁺ , ¹²⁰Ba , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁺, p , ¹¹⁹Cs , - , rowspan=2, ¹²¹La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 64 , rowspan=2, 120.93301(54)# , rowspan=2, 5.3(2) s , β⁺ , ¹²¹Ba , rowspan=2, 11/2−# , rowspan=2, , rowspan=2, , - , β⁺, p , ¹²⁰Cs , - , rowspan=2, ¹²²La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 65 , rowspan=2, 121.93071(32)# , rowspan=2, 8.6(5) s , β⁺ , ¹²²Ba , rowspan=2, , rowspan=2, , rowspan=2, , - , β⁺, p , ¹²¹Cs , - , ¹²³La , style="text-align:right" , 57 , style="text-align:right" , 66 , 122.92624(21)# , 17(3) s , β⁺ , ¹²³Ba , 11/2−# , , , - , ¹²⁴La , style="text-align:right" , 57 , style="text-align:right" , 67 , 123.92457(6) , 29.21(17) s , β⁺ , ¹²⁴Ba , (7−, 8−) , , , - , style="text-indent:1em" , ^124mLa , colspan="3" style="text-indent:2em" , 100(100)# keV , 21(4) s , , , low(+#) , , , - , ¹²⁵La , style="text-align:right" , 57 , style="text-align:right" , 68 , 124.920816(28) , 64.8(12) s , β⁺ , ¹²⁵Ba , (11/2−) , , , - , style="text-indent:1em" , ^125mLa , colspan="3" style="text-indent:2em" , 107.0(10) keV , 390(40) ms , , , (3/2+) , , , - , ¹²⁶La , style="text-align:right" , 57 , style="text-align:right" , 69 , 125.91951(10) , 54(2) s , β⁺ , ¹²⁶Ba , (5)(+#) , , , - , style="text-indent:1em" , ^126mLa , colspan="3" style="text-indent:2em" , 210(410) keV , 20(20) s , , , (0−, 1−, 2−) , , , - , ¹²⁷La , style="text-align:right" , 57 , style="text-align:right" , 70 , 126.916375(28) , 5.1(1) min , β⁺ , ¹²⁷Ba , (11/2−) , , , - , rowspan=2 style="text-indent:1em" , ^127mLa , rowspan=2 colspan="3" style="text-indent:2em" , 14.8(12) keV , rowspan=2, 3.7(4) min , β⁺ , ¹²⁷Ba , rowspan=2, (3/2+) , rowspan=2, , rowspan=2, , - , IT , ¹²⁷La , - , ¹²⁸La , style="text-align:right" , 57 , style="text-align:right" , 71 , 127.91559(6) , 5.18(14) min , β⁺ , ¹²⁸Ba , (5+) , , , - , style="text-indent:1em" , ^128mLa , colspan="3" style="text-indent:2em" , 100(100)# keV , <1.4 min , IT , ¹²⁸La , (1+, 2−) , , , - , ¹²⁹La , style="text-align:right" , 57 , style="text-align:right" , 72 , 128.912693(22) , 11.6(2) min , β⁺ , ¹²⁹Ba , 3/2+ , , , - , style="text-indent:1em" , ^129mLa , colspan="3" style="text-indent:2em" , 172.1(4) keV , 560(50) ms , IT , ¹²⁹La , 11/2− , , , - , ¹³⁰La , style="text-align:right" , 57 , style="text-align:right" , 73 , 129.912369(28) , 8.7(1) min , β⁺ , ''¹³⁰Ba'' , 3(+) , , , - , ¹³¹La , style="text-align:right" , 57 , style="text-align:right" , 74 , 130.91007(3) , 59(2) min , β⁺ , ¹³¹Ba , 3/2+ , , , - , style="text-indent:1em" , ^131mLa , colspan="3" style="text-indent:2em" , 304.52(24) keV , 170(10) μs , , , 11/2− , , , - , ¹³²La , style="text-align:right" , 57 , style="text-align:right" , 75 , 131.91010(4) , 4.8(2) h , β⁺ , ¹³²Ba , 2− , , , - , rowspan=2 style="text-indent:1em" , ^132mLa , rowspan=2 colspan="3" style="text-indent:2em" , 188.18(11) keV , rowspan=2, 24.3(5) min , IT (76%) , ¹³²La , rowspan=2, 6− , rowspan=2, , rowspan=2, , - , β⁺ (24%) , ¹³²Ba , - , ¹³³La , style="text-align:right" , 57 , style="text-align:right" , 76 , 132.90822(3) , 3.912(8) h , β⁺ , ¹³³Ba , 5/2+ , , , - , ¹³⁴La , style="text-align:right" , 57 , style="text-align:right" , 77 , 133.908514(21) , 6.45(16) min , β⁺ , ¹³⁴Ba , 1+ , , , - , ¹³⁵La , style="text-align:right" , 57 , style="text-align:right" , 78 , 134.906977(11) , 19.5(2) h , β⁺ , ¹³⁵Ba , 5/2+ , , , - , ¹³⁶La , style="text-align:right" , 57 , style="text-align:right" , 79 , 135.90764(6) , 9.87(3) min , β⁺ , ¹³⁶Ba , 1+ , , , - , style="text-indent:1em" , ^136mLa , colspan="3" style="text-indent:2em" , 255(9) keV , 114(3) ms , IT , ¹³⁶La , (8)(−#) , , , - , ¹³⁷La , style="text-align:right" , 57 , style="text-align:right" , 80 , 136.906494(14) , 6(2)×10⁴ y , EC , ¹³⁷Ba , 7/2+ , , ,

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

, - , rowspan=2, ¹³⁸La

Primordial Primordial may refer to: * Primordial era, an era after the Big Bang. See Chronology of the universe * Primordial sea (a.k.a. primordial ocean, ooze or soup). See Abiogenesis * Primordial nuclide, nuclides, a few radioactive, that formed before t ...

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...

, rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 81 , rowspan=2, 137.907112(4) , rowspan=2, 1.02(1)×10¹¹ y , β⁺ (66.4%) , ¹³⁸Ba , rowspan=2, 5+ , rowspan=2, 9.0(1)×10⁻⁴ , rowspan=2, , - , β⁻ (33.6%) , ¹³⁸Ce , - , style="text-indent:1em" , ^138mLa , colspan="3" style="text-indent:2em" , 72.57(3) keV , 116(5) ns , , , (3)+ , , , - , ¹³⁹La

Fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...

, style="text-align:right" , 57 , style="text-align:right" , 82 , 138.9063533(26) , colspan=3 align=center, StableTheoretically capable of

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakd ...

, 7/2+ , 0.99910(1) , , - , ¹⁴⁰La , style="text-align:right" , 57 , style="text-align:right" , 83 , 139.9094776(26) , 1.6781(3) d , β⁻ , ¹⁴⁰Ce , 3− , , , - , ¹⁴¹La , style="text-align:right" , 57 , style="text-align:right" , 84 , 140.910962(5) , 3.92(3) h , β⁻ , ¹⁴¹Ce , (7/2+) , , , - , ¹⁴²La , style="text-align:right" , 57 , style="text-align:right" , 85 , 141.914079(6) , 91.1(5) min , β⁻ , ¹⁴²Ce , 2− , , , - , ¹⁴³La , style="text-align:right" , 57 , style="text-align:right" , 86 , 142.916063(17) , 14.2(1) min , β⁻ , ¹⁴³Ce , (7/2)+ , , , - , ¹⁴⁴La , style="text-align:right" , 57 , style="text-align:right" , 87 , 143.91960(5) , 40.8(4) s , β⁻ , ¹⁴⁴Ce , (3−) , , , - , ¹⁴⁵La , style="text-align:right" , 57 , style="text-align:right" , 88 , 144.92165(10) , 24.8(20) s , β⁻ , ¹⁴⁵Ce , (5/2+) , , , - , rowspan=2, ¹⁴⁶La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 89 , rowspan=2, 145.92579(8) , rowspan=2, 6.27(10) s , β⁻ (99.99%) , ¹⁴⁶Ce , rowspan=2, 2− , rowspan=2, , rowspan=2, , - , β⁻, n (.007%) , ¹⁴⁵Ce , - , style="text-indent:1em" , ^146mLa , colspan="3" style="text-indent:2em" , 130(130) keV , 10.0(1) s , β⁻ , ¹⁴⁶Ce , (6−) , , , - , rowspan=2, ¹⁴⁷La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 90 , rowspan=2, 146.92824(5) , rowspan=2, 4.015(8) s , β⁻ (99.96%) , ¹⁴⁷Ce , rowspan=2, (5/2+) , rowspan=2, , rowspan=2, , - , β⁻, n (.04%) , ¹⁴⁶Ce , - , rowspan=2, ¹⁴⁸La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 91 , rowspan=2, 147.93223(6) , rowspan=2, 1.26(8) s , β⁻ (99.85%) , ¹⁴⁸Ce , rowspan=2, (2−) , rowspan=2, , rowspan=2, , - , β⁻, n (.15%) , ¹⁴⁷Ce , - , rowspan=2, ¹⁴⁹La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 92 , rowspan=2, 148.93473(34)# , rowspan=2, 1.05(3) s , β⁻ (98.6%) , ¹⁴⁹Ce , rowspan=2, 5/2+# , rowspan=2, , rowspan=2, , - , β⁻, n (1.4%) , ¹⁴⁸Ce , - , rowspan=2, ¹⁵⁰La , rowspan=2 style="text-align:right" , 57 , rowspan=2 style="text-align:right" , 93 , rowspan=2, 149.93877(43)# , rowspan=2, 510(30) ms , β⁻ (97.3%) , ¹⁵⁰Ce , rowspan=2, (3+) , rowspan=2, , rowspan=2, , - , β⁻, n (2.7%) , ¹⁴⁹Ce , - , ¹⁵¹La , style="text-align:right" , 57 , style="text-align:right" , 94 , 150.94172(43)# , 300# ms 300 ns, β⁻ , ¹⁵¹Ce , 5/2+# , , , - , ¹⁵²La , style="text-align:right" , 57 , style="text-align:right" , 95 , 151.94625(43)# , 200# ms 300 ns, β⁻ , ¹⁵²Ce , , , , - , ¹⁵³La , style="text-align:right" , 57 , style="text-align:right" , 96 , 152.94962(64)# , 150# ms 300 ns, β⁻ , ¹⁵³Ce , 5/2+# , , , - , ¹⁵⁴La , style="text-align:right" , 57 , style="text-align:right" , 97 , 153.95450(64)# , 100# ms , β⁻ , ¹⁵⁴Ce , , , , - , ¹⁵⁵La , style="text-align:right" , 57 , style="text-align:right" , 98 , 154.95835(86)# , 60# ms , β⁻ , ¹⁵⁵Ce , 5/2+# , ,

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Lanthanum

Lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between l ...