Isotopes of erbium

Isotopes of erbium (₆₈Er)
Standard atomic weight Ar°(Er)
	167.259±0.003; 167.26±0.01 (abridged)[2][3];

Naturally occurring erbium (₆₈Er) is composed of 6 stable isotopes, with ¹⁶⁶Er being the most abundant (33.503% natural abundance). 39 radioisotopes have been characterized with between 74 and 112 neutrons, or 142 to 180 nucleons, with the most stable being ¹⁶⁹Er with a half-life of 9.4 days, ¹⁷²Er with a half-life of 49.3 hours, ¹⁶⁰Er with a half-life of 28.58 hours, ¹⁶⁵Er with a half-life of 10.36 hours, and ¹⁷¹Er with a half-life of 7.516 hours. All of the remaining radioactive isotopes have half-lives that are less than 3.5 hours, and the majority of these have half-lives that are less than 4 minutes. This element also has numerous meta states, with the most stable being ^167mEr (t_1/2 2.269 seconds).

The isotopes of erbium range in atomic weight from 141.9723 u (¹⁴²Er) to 176.9541 u (¹⁷⁷Er). The primary decay mode before the most abundant stable isotope, ¹⁶⁶Er, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁶⁶Er are holmium isotopes, and the primary products after are thulium isotopes. All isotopes of erbium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6]	Spin and parity [n 7][n 4]	Natural abundance (mole fraction)
Nuclide [n 1]	Excitation energy[n 4]			Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6]	Spin and parity [n 7][n 4]	Normal proportion	Range of variation
¹⁴²Er	68	74	141.97002(54)#	10# μs	p	¹⁴¹Ho	0+
¹⁴³Er	68	75	142.96655(43)#	200# ms	β⁺	¹⁴³Ho	9/2−#
¹⁴³Er	68	75	142.96655(43)#	200# ms	β⁺, p	¹⁴²Dy	9/2−#
¹⁴⁴Er	68	76	143.96070(21)#	400# ms [>200 ns]	β⁺	¹⁴⁴Ho	0+
¹⁴⁵Er	68	77	144.95787(22)#	900(200) ms	β⁺	¹⁴⁵Ho	1/2+#
¹⁴⁵Er	68	77	144.95787(22)#	900(200) ms	β⁺, p (rare)	¹⁴⁴Dy	1/2+#
^145mEr	205(4)# keV			1.0(3) s	β⁺	¹⁴⁵Ho	(11/2-)
					IT (rare)	¹⁴⁵Er
					β⁺, p (rare)	¹⁴⁴Dy
¹⁴⁶Er	68	78	145.952418(7)	1.7(6) s	β⁺	¹⁴⁶Ho	0+
¹⁴⁶Er	68	78	145.952418(7)	1.7(6) s	β⁺, p (rare)	¹⁴⁵Dy	0+
¹⁴⁷Er	68	79	146.94996(4)#	3.2(1.2) s	β⁺	¹⁴⁷Ho	(1/2+)
¹⁴⁷Er	68	79	146.94996(4)#	3.2(1.2) s	β⁺, p (rare)	¹⁴⁶Dy	(1/2+)
^147mEr	100(50)# keV			1.6(2) s	β⁺	¹⁴⁷Ho	(11/2−)
^147mEr	100(50)# keV			1.6(2) s	β⁺, p (rare)	¹⁴⁶Dy	(11/2−)
¹⁴⁸Er	68	80	147.944735(11)#	4.6(2) s	β⁺ (99.85%)	¹⁴⁸Ho	0+
¹⁴⁸Er	68	80	147.944735(11)#	4.6(2) s	β⁺, p (.15%)	¹⁴⁷Dy	0+
^148mEr	2.9132(4) MeV			13(3) μs	IT	¹⁴⁸Er	(10+)
¹⁴⁹Er	68	81	148.94231(3)	4(2) s	β⁺ (92.8%)	¹⁴⁹Ho	(1/2+)
¹⁴⁹Er	68	81	148.94231(3)	4(2) s	β⁺, p (7.2%)	¹⁴⁸Dy	(1/2+)
^149m1Er	741.8(2) keV			8.9(2) s	β⁺ (96.5%)	¹⁴⁹Ho	(11/2−)
					IT (3.5%)	¹⁴⁹Er
					β⁺, p (.18%)	¹⁴⁸Dy
^149m2Er	2.6111(3) MeV			0.61(8) μs	IT	¹⁴⁹Er	(19/2+)
^149m3Er	3.302(7) MeV			4.8(1) μs	IT	¹⁴⁹Er	(27/2−)
¹⁵⁰Er	68	82	149.937916(18)	18.5(7) s	β⁺	¹⁵⁰Ho	0+
^150mEr	2.7965(5) MeV			2.55(10) μs	IT	¹⁵⁰Er	10+
¹⁵¹Er	68	83	150.937449(18)	23.5(20) s	β⁺	¹⁵¹Ho	(7/2−)
^151m1Er	2.5860(5) MeV			580(20) ms	IT (95.3%)	¹⁵¹Er	(27/2−)
^151m1Er	2.5860(5) MeV			580(20) ms	β⁺ (4.7%)	¹⁵¹Ho	(27/2−)
^151m2Er	10.2866(10) MeV			0.42(5) μs	IT	¹⁵¹Er	(65/2-, 61/2+)
¹⁵²Er	68	84	151.935050(9)	10.3(1) s	α (90%)	¹⁴⁸Dy	0+
¹⁵²Er	68	84	151.935050(9)	10.3(1) s	β⁺ (10%)	¹⁵²Ho	0+
¹⁵³Er	68	85	152.935086(10)	37.1(2) s	α (53%)	¹⁴⁹Dy	7/2(−)
¹⁵³Er	68	85	152.935086(10)	37.1(2) s	β⁺ (47%)	¹⁵³Ho	7/2(−)
^153m1Er	2.7982(10) MeV			373(9) ns	IT	¹⁵³Er	(27/2-)
^153m2Er	5.2481(10) MeV			248(32) ns	IT	¹⁵³Er	(41/2-)
¹⁵⁴Er	68	86	153.932791(5)	3.73(9) min	β⁺ (99.53%)	¹⁵⁴Ho	0+
¹⁵⁴Er	68	86	153.932791(5)	3.73(9) min	α (.47%)	¹⁵⁰Dy	0+
¹⁵⁵Er	68	87	154.933216(7)	5.3(3) min	β⁺ (99.978%)	¹⁵⁵Ho	7/2−
¹⁵⁵Er	68	87	154.933216(7)	5.3(3) min	α (.022%)	¹⁵¹Dy	7/2−
¹⁵⁶Er	68	88	155.931066(26)	19.5(10) min	β⁺	¹⁵⁶Ho	0+
¹⁵⁶Er	68	88	155.931066(26)	19.5(10) min	α (1.2×10⁻⁵%)	¹⁵²Dy	0+
¹⁵⁷Er	68	89	156.931923(28)	18.65(10) min	β⁺	¹⁵⁷Ho	3/2−
^157mEr	155.4(3) keV			76(6) ms	IT	¹⁵⁷Er	(9/2+)
¹⁵⁸Er	68	90	157.929893(27)	2.29(6) h	EC	¹⁵⁸Ho	0+
¹⁵⁹Er	68	91	158.930691(4)	36(1) min	β⁺	¹⁵⁹Ho	3/2−
^159m1Er	182.602(24) keV			337(14) ns	IT	¹⁵⁹Er	9/2+
^159m2Er	429.05(3) keV			590(60) ns	IT	¹⁵⁹Er	11/2−
¹⁶⁰Er	68	92	159.929077(26)	28.58(9) h	EC	¹⁶⁰Ho	0+
¹⁶¹Er	68	93	160.930004(9)	3.21(3) h	β⁺	¹⁶¹Ho	3/2−
^161mEr	396.44(4) keV			7.5(7) μs	IT	¹⁶¹Er	11/2−
¹⁶²Er	68	94	161. 9287873(8)	Observationally Stable[n 8]			0+	0.00139(5)
^162mEr	2.02601(13) MeV			88(16) ns	IT	¹⁶²Er	(7-)
¹⁶³Er	68	95	162.930040(5)	75.0(4) min	β⁺	¹⁶³Ho	5/2−
^163mEr	445.5(6) keV			580(100) ns	IT	¹⁶³Er	(11/2−)
¹⁶⁴Er	68	96	163.9292077(8)	Observationally Stable[n 9]			0+	0.01601(3)
¹⁶⁵Er	68	97	164.9307335(10)	10.36(4) h	EC	¹⁶⁵Ho	5/2−
^165m1Er	551.3(6) keV			250(30)ns	IT	¹⁶⁵Er	11/2-
^165m2Er	1.8230(6) MeV			370(40)ns	IT	¹⁶⁵Er	(19/2)
¹⁶⁶Er	68	98	165.9303011(4)	Observationally Stable[n 10]			0+	0.33503(36)
¹⁶⁷Er	68	99	166.9320562(3)	Observationally Stable[n 11]			7/2+	0.22869(9)
^167mEr	207.801(5) keV			2.269(6) s	IT	¹⁶⁷Er	1/2−
¹⁶⁸Er	68	100	167.93237828(28)	Observationally Stable[n 12]			0+	0.26978(18)
^168mEr	1.0940383(16) MeV			109.0(7) ns	IT	¹⁶⁸Er	4-
¹⁶⁹Er	68	101	168.9345984(3)	9.392(18) d	β⁻	¹⁶⁹Tm	1/2−
^169m1Er	92.05(10) keV			285(20) ns	IT	¹⁶⁹Er	(5/2-)
^169m2Er	243.69(17) keV			200(10) ns	IT	¹⁶⁹Er	7/2+
¹⁷⁰Er	68	102	169.9354719(15)	Observationally Stable[n 13]			0+	0.14910(36)
¹⁷¹Er	68	103	170.93803746(15)	7.516(2) h	β⁻	¹⁷¹Tm	5/2−
^171mEr	198.61(9) keV\|			210(10) ns	IT	¹⁷¹Er	1/2−
¹⁷²Er	68	104	171. 939363(4)	49.3(5) h	β⁻	¹⁷²Tm	0+
^172mEr	1.5009(3) MeV			579(62) ns	IT	¹⁷²Er	(6+)
¹⁷³Er	68	105	172.94240(21)#	1.434(17) min	β⁻	¹⁷³Tm	(7/2−)
¹⁷⁴Er	68	106	173.94423(32)#	3.2(2) min	β⁻	¹⁷⁴Tm	0+
^174mEr	1.1115(7) MeV			3.9(3) s	IT	¹⁷⁴Er	8-
¹⁷⁵Er	68	107	174.94777(43)#	1.2(3) min	β⁻	¹⁷⁵Tm	9/2+#
¹⁷⁶Er	68	108	175.94994(43)#	12# s (>300 ns)	β⁻	¹⁷⁶Tm	0+
¹⁷⁷Er	68	109	176.95399(54)#	8# s (>300 ns)	β⁻	¹⁷⁷Tm	1/2−#
¹⁷⁸Er	68	110	177.95678(64)#	4# s (>300 ns)	β⁻	¹⁷⁸Tm	0+
¹⁷⁹Er	68	111	178.96127(54)#	3# s (>550 ns)	β⁻	¹⁷⁹Tm	3/2−#
¹⁷⁹Er	68	111	178.96127(54)#	3# s (>550 ns)	β⁻, n	¹⁷⁸Tm	3/2−#
¹⁸⁰Er	68	112	179.96438(54)#	2# s (>550 ns)	β⁻	¹⁸⁰Tm	0+
¹⁸⁰Er	68	112	179.96438(54)#	2# s (>550 ns)	β⁻, n	¹⁷⁹Tm	0+
This table header & footer:

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

EC: Electron capture

IT: Isomeric transition

p: Proton emission
Bold symbol as daughter – Daughter product is stable.
( ) spin value – Indicates spin with weak assignment arguments.
Believed to undergo α decay to ¹⁵⁸Dy or β⁺β⁺ to ¹⁶²Dy with a half-life over 140×10¹² years
Believed to undergo α decay to ¹⁶⁰Dy or β⁺β⁺ to ¹⁶⁴Dy
Believed to undergo α decay to ¹⁶²Dy
Believed to undergo α decay to ¹⁶³Dy
Believed to undergo α decay to ¹⁶⁴Dy
Believed to undergo α decay to ¹⁶⁶Dy or β⁻β⁻ to ¹⁷⁰Yb with a half-life over 410×10¹⁵ years

Erbium-169

The radioactive isotope erbium-169 is sometimes used in radiopharmaceuticals.

References

Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
"Standard Atomic Weights: Erbium". CIAAW. 1999.
Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

Isotope masses from:
- Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
Isotopic compositions and standard atomic masses from:
- Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.

"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

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[4] Er – Excited nuclear isomer.

[5] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-6] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[TNN-7] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[8] Modes of decay:

EC: Electron capture

IT: Isomeric transition

p: Proton emission

[9] Bold symbol as daughter – Daughter product is stable.

[10] ( ) spin value – Indicates spin with weak assignment arguments.

[11] Believed to undergo α decay to ¹⁵⁸Dy or β⁺β⁺ to ¹⁶²Dy with a half-life over 140×10¹² years

[12] Believed to undergo α decay to ¹⁶⁰Dy or β⁺β⁺ to ¹⁶⁴Dy

[13] Believed to undergo α decay to ¹⁶²Dy

[14] Believed to undergo α decay to ¹⁶³Dy

[15] Believed to undergo α decay to ¹⁶⁴Dy

[16] Believed to undergo α decay to ¹⁶⁶Dy or β⁻β⁻ to ¹⁷⁰Yb with a half-life over 410×10¹⁵ years

[NUBASE2020-1] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[2] "Standard Atomic Weights: Erbium". CIAAW. 1999.

[CIAAW2021-3] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.