Isotopes of lanthanum

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

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)
nuclide symbol	excitation energy			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)
¹¹⁷La	57	60	116.95007(43)#	23.5(26) ms	β⁺	¹¹⁷Ba	(3/2+,3/2−)
¹¹⁷La	57	60	116.95007(43)#	23.5(26) ms	p	¹¹⁶Ba	(3/2+,3/2−)
^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
¹²⁰La	57	63	119.93807(54)#	2.8(2) s	β⁺, p	¹¹⁹Cs
¹²¹La	57	64	120.93301(54)#	5.3(2) s	β⁺	¹²¹Ba	11/2−#
¹²¹La	57	64	120.93301(54)#	5.3(2) s	β⁺, p	¹²⁰Cs	11/2−#
¹²²La	57	65	121.93071(32)#	8.6(5) s	β⁺	¹²²Ba
¹²²La	57	65	121.93071(32)#	8.6(5) s	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+)
^127mLa	14.8(12) keV			3.7(4) min	IT	¹²⁷La	(3/2+)
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−
^132mLa	188.18(11) keV			24.3(5) min	β⁺ (24%)	¹³²Ba	6−
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	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
¹³⁸La^{[n 4]}	57	81	137.907112(4)	1.02(1)×10¹¹ a	β^- (33.6%)	¹³⁸Ce	5+	9.0(1)×10⁻⁴
^138mLa	72.57(3) keV			116(5) ns			(3)+
¹³⁹La^{[n 5]}	57	82	138.9063533(26)	Observationally 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−
¹⁴⁶La	57	89	145.92579(8)	6.27(10) s	β^-, n (.007%)	¹⁴⁵Ce	2−
^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+)
¹⁴⁷La	57	90	146.92824(5)	4.015(8) s	β^-, n (.04%)	¹⁴⁶Ce	(5/2+)
¹⁴⁸La	57	91	147.93223(6)	1.26(8) s	β^- (99.85%)	¹⁴⁸Ce	(2−)
¹⁴⁸La	57	91	147.93223(6)	1.26(8) s	β^-, n (.15%)	¹⁴⁷Ce	(2−)
¹⁴⁹La	57	92	148.93473(34)#	1.05(3) s	β^- (98.6%)	¹⁴⁹Ce	5/2+#
¹⁴⁹La	57	92	148.93473(34)#	1.05(3) s	β^-, n (1.4%)	¹⁴⁸Ce	5/2+#
¹⁵⁰La	57	93	149.93877(43)#	510(30) ms	β^- (97.3%)	¹⁵⁰Ce	(3+)
¹⁵⁰La	57	93	149.93877(43)#	510(30) ms	β^-, n (2.7%)	¹⁴⁹Ce	(3+)
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+#

^ Bold for isotopes with half-lives longer than the age of the universe (nearly stable)
^ Abbreviations:
EC: Electron capture
IT: Isomeric transition
^ Bold for stable isotopes, bold italics for near-stable isotopes (half-life longer than the age of the universe)
^ Primordial radionuclide
^ ^a ^b Fission product
^ Theoretically capable of spontaneous fission

Notes

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

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

Isotope masses from:
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
Isotopic compositions and standard atomic masses from:
- J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. http://www.iupac.org/publications/pac/75/6/0683/pdf/.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. http://iupac.org/publications/pac/78/11/2051/pdf/. Lay summary.
Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
- G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved September 2005.
- N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0849304859.

Isotopes of barium	Isotopes of lanthanum	Isotopes of cerium
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