Isotopes of lanthanum

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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 isomers, 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

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life[n 1] decay
mode(s)[1][n 2]
daughter
isotope(s)[n 3]
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+ 117Ba (3/2+,3/2−)
p 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 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)×104 a EC 137Ba 7/2+
138La[n 4] 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)+
139La[n 5] 57 82 138.9063533(26) Stable[n 6] 7/2+ 0.99910(1)
140La[n 5] 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 (.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+#
  1. ^ Bold for isotopes with half-lives longer than the age of the universe (nearly stable)
  2. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  3. ^ Bold for stable isotopes, bold italics for near-stable isotopes (half-life longer than the age of the universe)
  4. ^ Primordial radionuclide
  5. ^ a b Fission product
  6. ^ Theoretically capable of spontaneous fission

Notes[edit]

  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  1. ^ http://www.nucleonica.net/unc.aspx


Isotopes of barium Isotopes of lanthanum Isotopes of cerium
Table of nuclides