Isotopes of lanthanum
Encyclopedia
Naturally occurring lanthanum
(La) is composed of one stable (139La) and one radioactive (138La) isotope
, with the stable isotope, 139La, being the most abundant (99.91% natural abundance
). 38 radioisotopes have been characterized with the most stable being 138La with a half-life
of 102×109 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
s, the longest-lived of which is 132mLa with a half-life of 24.3 minutes.
The isotopes of lanthanum range in atomic weight
from 116.95 u
(117La) to 154.96 u (155La).
Standard atomic mass: 138.90547(7) u
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
(La) is composed of one stable (139La) and one radioactive (138La) isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
, with the stable isotope, 139La, being the most abundant (99.91% natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...
). 38 radioisotopes have been characterized with the most stable being 138La with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 102×109 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
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
s, the longest-lived of which is 132mLa with a half-life of 24.3 minutes.
The isotopes of lanthanum range in atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
from 116.95 u
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
(117La) to 154.96 u (155La).
Standard atomic mass: 138.90547(7) u
Table
| nuclide symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-lifeBold for isotopes with half-lives longer than the age of the universe (nearly stable) | decay mode(s)Abbreviations: EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
daughter isotope(s)Bold for stable isotopes, bold italics for near-stable isotopes (half-life longer than the age of the universe Age of the universe The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model... ) |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 117La | 57 | 60 | 116.95007(43)# | 23.5(26) ms | β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... |
117Ba | (3/2+,3/2−) | ||
| p Proton emission Proton emission is a type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state of very... |
116Ba | ||||||||
| 117mLa | 151(12) keV | 10(5) ms | (9/2+) | ||||||
| 118La | 57 | 61 | 117.94673(32)# | 200# ms | β+ | 118Ba | |||
| 119La | 57 | 62 | 118.94099(43)# | 1# s | β+ | 119Ba | 11/2−# | ||
| 120La | 57 | 63 | 119.93807(54)# | 2.8(2) s | β+ | 120Ba | |||
| β+, p | 119Cs | ||||||||
| 121La | 57 | 64 | 120.93301(54)# | 5.3(2) s | β+ | 121Ba | 11/2−# | ||
| β+, p | 120Cs | ||||||||
| 122La | 57 | 65 | 121.93071(32)# | 8.6(5) s | β+ | 122Ba | |||
| β+, p | 121Cs | ||||||||
| 123La | 57 | 66 | 122.92624(21)# | 17(3) s | β+ | 123Ba | 11/2−# | ||
| 124La | 57 | 67 | 123.92457(6) | 29.21(17) s | β+ | 124Ba | (7−,8−) | ||
| 124mLa | 100(100)# keV | 21(4) s | low(+#) | ||||||
| 125La | 57 | 68 | 124.920816(28) | 64.8(12) s | β+ | 125Ba | (11/2−) | ||
| 125mLa | 107.0(10) keV | 390(40) ms | (3/2+) | ||||||
| 126La | 57 | 69 | 125.91951(10) | 54(2) s | β+ | 126Ba | (5)(+#) | ||
| 126mLa | 210(410) keV | 20(20) s | (0−,1−,2−) | ||||||
| 127La | 57 | 70 | 126.916375(28) | 5.1(1) min | β+ | 127Ba | (11/2−) | ||
| 127mLa | 14.8(12) keV | 3.7(4) min | β+ | 127Ba | (3/2+) | ||||
| IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
127La | ||||||||
| 128La | 57 | 71 | 127.91559(6) | 5.18(14) min | β+ | 128Ba | (5+) | ||
| 128mLa | 100(100)# keV | <1.4 min | IT | 128La | (1+,2−) | ||||
| 129La | 57 | 72 | 128.912693(22) | 11.6(2) min | β+ | 129Ba | 3/2+ | ||
| 129mLa | 172.1(4) keV | 560(50) ms | IT | 129La | 11/2− | ||||
| 130La | 57 | 73 | 129.912369(28) | 8.7(1) min | β+ | 130Ba | 3(+) | ||
| 131La | 57 | 74 | 130.91007(3) | 59(2) min | β+ | 131Ba | 3/2+ | ||
| 131mLa | 304.52(24) keV | 170(10) µs | 11/2− | ||||||
| 132La | 57 | 75 | 131.91010(4) | 4.8(2) h | β+ | 132Ba | 2− | ||
| 132mLa | 188.18(11) keV | 24.3(5) min | IT (76%) | 132La | 6− | ||||
| β+ (24%) | 132Ba | ||||||||
| 133La | 57 | 76 | 132.90822(3) | 3.912(8) h | β+ | 133Ba | 5/2+ | ||
| 134La | 57 | 77 | 133.908514(21) | 6.45(16) min | β+ | 134Ba | 1+ | ||
| 135La | 57 | 78 | 134.906977(11) | 19.5(2) h | β+ | 135Ba | 5/2+ | ||
| 136La | 57 | 79 | 135.90764(6) | 9.87(3) min | β+ | 136Ba | 1+ | ||
| 136mLa | 255(9) keV | 114(3) ms | IT | 136La | (8)(−#) | ||||
| 137La | 57 | 80 | 136.906494(14) | 6(2)E×104 a | EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... |
137Ba | 7/2+ | ||
| 138LaPrimordial Primordial nuclide In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known... radionuclide Radionuclide A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma... |
57 | 81 | 137.907112(4) | 1.02(1)×1011 a | β+ (66.4%) | 138Ba | 5+ | 9.0(1)×10−4 | |
| β- (33.6%) | 138Ce | ||||||||
| 138mLa | 72.57(3) keV | 116(5) ns | (3)+ | ||||||
| 139LaFission product Fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The... |
57 | 82 | 138.9063533(26) | Observationally StableTheoretically capable of spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... |
7/2+ | 0.99910(1) | |||
| 140La | 57 | 83 | 139.9094776(26) | 1.6781(3) d | β- | 140Ce | 3− | ||
| 141La | 57 | 84 | 140.910962(5) | 3.92(3) h | β- | 141Ce | (7/2+) | ||
| 142La | 57 | 85 | 141.914079(6) | 91.1(5) min | β- | 142Ce | 2− | ||
| 143La | 57 | 86 | 142.916063(17) | 14.2(1) min | β- | 143Ce | (7/2)+ | ||
| 144La | 57 | 87 | 143.91960(5) | 40.8(4) s | β- | 144Ce | (3−) | ||
| 145La | 57 | 88 | 144.92165(10) | 24.8(20) s | β- | 145Ce | (5/2+) | ||
| 146La | 57 | 89 | 145.92579(8) | 6.27(10) s | β- (99.99%) | 146Ce | 2− | ||
| β-, n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... (.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+# | ||
| 154La | 57 | 97 | 153.95450(64)# | 100# ms | β- | 154Ce | |||
| 155La | 57 | 98 | 154.95835(86)# | 60# ms | β- | 155Ce | 5/2+# | ||