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 lant ...

(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 numb ...

, with the stable isotope, ¹³⁹La, being the most abundant (99.91%

natural abundance In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomi ...

). 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 at ...

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 , - , rowspan=2, ¹³⁸La Primordial radionuclide , 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 , style="text-align:right" , 57 , style="text-align:right" , 82 , 138.9063533(26) , colspan=3 align=center, StableTheoretically capable of spontaneous fission , 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 lant ...