Isotopes of erbium

Naturally occurring erbium (Er) is composed of 6 stable isotopes, ¹⁶²Er, ¹⁶⁴Er, ¹⁶⁶Er, ¹⁶⁷Er, ¹⁶⁸Er, and ¹⁷⁰Er with ¹⁶⁶Er being the most abundant (33.503% natural abundance). Thirty radioisotopes have been characterized with between 74 and 108 neutrons, or 142 to 177 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 13 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.

Relative atomic mass: 167.259(3).

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[1][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
^142Er	68	74	141.97231(47)#				0+
^143Er	68	75	142.96634(64)#	200# ms			9/2−#
^144Er	68	76	143.96038(43)#	400# ms [>200 ns]	β^+	^144Ho	0+
^145Er	68	77	144.95739(43)#	900(300) ms	β^+	^145Ho	1/2+#
					β^+, p (rare)	^144Dy
^146Er	68	78	145.95200(32)#	1.7(6) s	β^+	^146Ho	0+
					β^+, p	^145Dy
^147Er	68	79	146.94949(32)#	~2.5 s	β^+	^147Ho	(1/2+)
					β^+, p	^146Dy
^147mEr	100(50)# keV			2.5(2) s	β^+	^147Ho	(11/2−)
^148Er	68	80	147.94455(21)#	4.6(2) s	β^+ (99.85%)	^148Ho	0+
					β^+, p (.15%)	^147Dy
^149Er	68	81	148.94231(3)	4(2) s	β^+ (93%)	^149Ho	(1/2+)
					β^+, p (7%)	^148Dy
^149m1Er	741.8(2) keV			8.9(2) s	β^+ (96.5%)	^149Ho	(11/2−)
					IT (3.5%)	^149Er
					β^+, p (.18%)	^148Dy
^149m2Er	2611.1(3) keV			0.61(8) µs			(19/2+)
^149m3Er	3242.7+X keV			4.8(1) µs			(27/2−)
^150Er	68	82	149.937914(18)	18.5(7) s	β^+	^150Ho	0+
^151Er	68	83	150.937449(18)	23.5(13) s	β^+	^151Ho	(7/2−)
^151m1Er	2585.5(6) keV			580(20) ms	IT (95.3%)	^151Er	(27/2−)
					β^+ (4.7%)	^151Ho
^151m2Er	10286+X keV			0.42(5) µs			(67/2,69/2,71/2)
^152Er	68	84	151.935050(11)	10.3(1) s	α (90%)	^148Dy	0+
					β^+ (10%)	^152Ho
^153Er	68	85	152.935063(9)	37.1(2) s	α (53%)	^149Dy	7/2(−)
					β^+ (47%)	^153Ho
^154Er	68	86	153.932783(6)	3.73(9) min	β^+ (99.53%)	^154Ho	0+
					α (.47%)	^150Dy
^155Er	68	87	154.933209(7)	5.3(3) min	β^+ (99.98%)	^155Ho	7/2−
					α (.022%)	^151Dy
^156Er	68	88	155.931065(26)	19.5(10) min	β^+	^156Ho	0+
^157Er	68	89	156.93192(3)	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	158.930684(5)	36(1) min	β^+	^159Ho	3/2−
^159m1Er	182.602(24) keV			337(14) ns			9/2+
^159m2Er	429.05(3) keV			590(60) ns			11/2−
^160Er	68	92	159.929083(26)	28.58(9) h	EC	^160Ho	0+
^161Er	68	93	160.929995(10)	3.21(3) h	β^+	^161Ho	3/2−
^161mEr	396.44(4) keV			7.5(7) µs			11/2−
^162Er	68	94	161.928778(4)	Observationally Stable[n 3]			0+	0.00139(5)
^163Er	68	95	162.930033(6)	75.0(4) min	β^+	^163Ho	5/2−
^163mEr	445.5(6) keV			580(100) ns			(11/2−)
^164Er	68	96	163.929200(3)	Observationally Stable[n 4]			0+	0.01601(3)
^165Er	68	97	164.930726(3)	10.36(4) h	EC	^165Ho	5/2−
^166Er	68	98	165.9302931(27)	Observationally Stable[n 5]			0+	0.33503(36)
^167Er	68	99	166.9320482(27)	Observationally Stable[n 6]			7/2+	0.22869(9)
^167mEr	207.801(5) keV			2.269(6) s	IT	^167Er	1/2−
^168Er	68	100	167.9323702(27)	Observationally Stable[n 7]			0+	0.26978(18)
^169Er	68	101	168.9345904(27)	9.392(18) d	β^−	^169Tm	1/2−
^170Er	68	102	169.9354643(30)	Observationally Stable[n 8]			0+	0.14910(36)
^171Er	68	103	170.9380298(30)	7.516(2) h	β^−	^171Tm	5/2−
^171mEr	198.6(1) keV			210(10) ns			1/2−
^172Er	68	104	171.939356(5)	49.3(3) h	β^−	^172Tm	0+
^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+
^175Er	68	107	174.94777(43)#	1.2(3) min	β^−	^175Tm	(9/2+)
^176Er	68	108	175.95008(43)#	20# s	β^−	^176Tm	0+
^177Er	68	109	176.95405(54)#	3# s	β^−	^177Tm	1/2−#

1. Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. Bold for stable isotopes
3. Believed to undergo α decay to ¹⁵⁸Dy or β⁺β⁺ to ¹⁶²Dy with a half-life over 140×10¹² years
4. Believed to undergo α decay to ¹⁶⁰Dy or β⁺β⁺ to ¹⁶⁴Dy
5. Believed to undergo α decay to ¹⁶²Dy
6. Believed to undergo α decay to ¹⁶³Dy
7. Believed to undergo α decay to ¹⁶⁴Dy
8. Believed to undergo α decay to ¹⁶⁶Dy or β⁻β⁻ to ¹⁷⁰Yb with a half-life over 320×10¹⁵ years

References

1. "Universal Nuclide Chart". nucleonica. (registration required (help)).

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
• 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; 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.
  • 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. 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; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. 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 978-0-8493-0485-9.