Isotopes of cerium

Naturally occurring cerium (₅₈Ce) is composed of 4 stable isotopes: ¹³⁶Ce, ¹³⁸Ce, ¹⁴⁰Ce, and ¹⁴²Ce, with ¹⁴⁰Ce being the most abundant (88.45% natural abundance) and the only one that is theoretically stable. The others, ¹³⁶Ce, ¹³⁸Ce, and ¹⁴²Ce are predicted to undergo double beta decay, which has never been observed. There are 35 radioisotopes that have been characterized, with the most stable being ¹⁴⁴Ce, with a half-life of 284.89 days; ¹³⁹Ce, with a half-life of 137.64 days and ¹⁴¹Ce, with a half-life of 32.505 days. All of the remaining radioactive isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than 10 minutes.

Isotopes of cerium (₅₈Ce)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 134Ce synth 3.16 d ε 134La 136Ce 0.186% stable 138Ce 0.251% stable 139Ce synth 137.64 d ε 139La 140Ce 88.4% stable 141Ce synth 32.505 d β− 141Pr 142Ce 11.1% stable 143Ce synth 33.039 h β− 143Pr 144Ce synth 284.89 d β− 144Pr
Standard atomic weight Ar°(Ce)
	140.116±0.001[2] 140.12±0.01 (abridged)[3]
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The known isotopes of cerium range from ¹²¹Ce to ¹⁵⁷Ce, in addition to 14 meta states.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[4] [n 2][n 3]	Half-life[1] [n 4]	Decay mode[1] [n 5]	Daughter isotope [n 6]	Spin and parity[1] [n 7][n 4]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion[1]	Range of variation
121Ce	58	63	120.94344(43)#	1.1(1) s	β+ (99%)	121La	5/2(+#)
					β+, p (1%)	120Ba
122Ce	58	64	121.93787(43)#	2# s	β+	122La	0+
123Ce	58	65	122.93528(32)#	3.8(2) s	β+ (?%)	123La	(5/2)(+#)
					β+, p (?%)	122Ba
124Ce	58	66	123.93031(32)#	9.1(12) s	β+	124La	0+
125Ce	58	67	124.92844(21)#	9.7(3) s	β+ (?%)	125La	(7/2−)
					β+, p (?%)	124Ba
125mCe	93.6(4) keV			13(10) s	IT	125Ce	(1/2+)
126Ce	58	68	125.923971(30)	51.0(3) s	β+	126La	0+
127Ce	58	69	126.922727(31)	34(2) s	β+	127La	(1/2+)
127m1Ce	7.3(11) keV			28.6(7) s	β+	127La	(5/2+)
127m2Ce	36.9(11) keV			>10 μs	IT	127Ce	(7/2−)
128Ce	58	70	127.918911(30)	3.93(2) min	β+	128La	0+
129Ce	58	71	128.918102(30)	3.5(3) min	β+	129La	(5/2+)
130Ce	58	72	129.914736(30)	22.9(5) min	β+	130La	0+
130mCe	2453.6(3) keV			100(8) ns	IT	130Ce	7−
131Ce	58	73	130.914429(35)	10.3(3) min	β+	131La	7/2+
131mCe	63.09(9) keV			5.4(4) min	β+	131La	(1/2+)
132Ce	58	74	131.911466(22)	3.51(11) h	β+	132La	0+
132mCe	2341.15(21) keV			9.4(3) ms	IT	132Ce	8−
133Ce	58	75	132.911520(18)	97(4) min	β+	133La	1/2+
133mCe	37.2(7) keV			5.1(3) h	β+	133La	9/2−
134Ce	58	76	133.908928(22)	3.16(4) d	EC	134La	0+
134mCe	3208.6(4) keV			308(5) ns	IT	134Ce	10+
135Ce	58	77	134.909161(11)	17.7(3) h	β+	135La	1/2+
135mCe	445.81(21) keV			20(1) s	IT	135Ce	(11/2−)
136Ce	58	78	135.90712926(35)	Observationally stable[n 8]			0+	0.00186(2)
136mCe	3095.0(6) keV			1.96(9) μs	IT	136Ce	10+
137Ce	58	79	136.90776242(39)	9.0(3) h	β+	137La	3/2+
137mCe	254.29(5) keV			34.4(3) h	IT (99.21%)	137Ce	11/2−
					β+ (0.79%)	137La
138Ce	58	80	137.90599418(54)	Observationally stable[n 9]			0+	0.00251(2)
138mCe	2129.28(12) keV			8.73(20) ms	IT	138Ce	7-
139Ce	58	81	138.9066470(22)	137.642(20) d	EC	139La	3/2+
139mCe	754.24(8) keV			57.58(32) s	IT	139Ce	11/2−
140Ce[n 10]	58	82	139.9054484(14)	Stable			0+	0.88449(51)
140mCe	2107.854(24) keV			7.3(15) μs	IT	140Ce	6+
141Ce[n 10]	58	83	140.9082860(14)	32.505(10) d	β−	141Pr	7/2−
142Ce[n 10]	58	84	141.9092502(26)	Observationally stable[n 11][5]			0+	0.11114(51)
143Ce[n 10]	58	85	142.9123920(26)	33.039(6) h	β−	143Pr	3/2−
144Ce[n 10]	58	86	143.9136528(30)	284.886(25) d	β−	144Pr	0+
145Ce	58	87	144.917265(36)	3.01(6) min	β−	145Pr	5/2−#
146Ce	58	88	145.918812(16)	13.49(16) min	β−	146Pr	0+
147Ce	58	89	146.9226899(92)	56.4(10) s	β−	147Pr	(5/2−)
148Ce	58	90	147.924424(12)	56.8(3) s	β−	148Pr	0+
149Ce	58	91	148.928427(11)	4.94(4) s	β−	149Pr	3/2−#
150Ce	58	92	149.930384(13)	6.05(7) s	β−	150Pr	0+
151Ce	58	93	150.934272(19)	1.76(6) s	β−	151Pr	(3/2−)
152Ce	58	94	151.93668(22)#	1.42(2) s	β−	152Pr	0+
153Ce	58	95	152.94105(22)#	865(25) ms	β−	153Pr	3/2−#
154Ce	58	96	153.94394(22)#	722(14) ms	β−	154Pr	0+
155Ce	58	97	154.94871(32)#	313(7) ms	β−	155Pr	5/2−#
156Ce	58	98	155.95188(32)#	233(9) ms	β−	156Pr	0+
157Ce	58	99	156.95713(43)#	175(41) ms	β−	157Pr	7/2+#
158Ce	58	100	157.96077(43)#	99(93) ms	β−	158Pr	0+
This table header & footer: view

1. ^mCe – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.
8. Theorized to undergo β⁺β⁺ decay to ¹³⁶Ba with a half-life over 3.2×10¹⁶ years
9. Theorized to undergo β⁺β⁺ decay to ¹³⁸Ba with a half-life over 4.4×10¹⁶ years
10. Fission product
11. Theorized to undergo β⁻β⁻ decay to ¹⁴²Nd or α decay to ¹³⁸Ba with a half-life over 2.9×10¹⁸ years

See also

Daughter products other than cerium

• Isotopes of praseodymium
• Isotopes of lanthanum
• Isotopes of barium