Isotopes of hafnium

Natural hafnium (₇₂Hf) consists of five observationally stable isotopes (¹⁷⁶Hf, ¹⁷⁷Hf, ¹⁷⁸Hf, ¹⁷⁹Hf, and ¹⁸⁰Hf) and one very long-lived radioisotope, ¹⁷⁴Hf, with a half-life of 7.0×10¹⁶ years.^[2] In addition, there are 34 known synthetic radioisotopes, the most stable of which is ¹⁸²Hf with a half-life of 8.9×10⁶ years. This extinct radionuclide is used in hafnium–tungsten dating to study the chronology of planetary differentiation.^[5]

Isotopes of hafnium (₇₂Hf)

Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 172Hf synth 1.87 y ε 172Lu 174Hf 0.16% 7.0×1016 y[2] α 170Yb 176Hf 5.26% stable 177Hf 18.6% stable 178Hf 27.3% stable 178m2Hf synth 31 y IT 178Hf 179Hf 13.6% stable 180Hf 35.1% stable 182Hf synth 8.9×106 y β− 182Ta
Standard atomic weight Ar°(Hf)
	178.486±0.006[3] 178.49±0.01 (abridged)[4]
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No other radioisotope has a half-life over 1.87 years. Most isotopes have half-lives under 1 minute. There are also at least 27 nuclear isomers, the most stable of which is ^178m2Hf with a half-life of 31 years. All isotopes of hafnium 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][n 5]	Decay mode [n 6]	Daughter isotope [n 7]	Spin and parity [n 8][n 5]	Natural abundance (mole fraction)
	Excitation energy[n 5]							Normal proportion	Range of variation
153Hf	72	81	152.97069(54)#	400# ms [>200 ns]			1/2+#
153mHf	750(100)# keV			500# ms			11/2−#
154Hf	72	82	153.96486(54)#	2(1) s	β+	154Lu	0+
					α (rare)	150Yb
155Hf	72	83	154.96339(43)#	890(120) ms	β+	155Lu	7/2−#
					α (rare)	151Yb
156Hf	72	84	155.95936(22)	23(1) ms	α (97%)	152Yb	0+
					β+ (3%)	156Lu
156mHf	1959.0(10) keV			480(40) μs			8+
157Hf	72	85	156.95840(21)#	115(1) ms	α (86%)	153Yb	7/2−
					β+ (14%)	157Lu
158Hf	72	86	157.954799(19)	2.84(7) s	β+ (55%)	158Lu	0+
					α (45%)	154Yb
159Hf	72	87	158.953995(18)	5.20(10) s	β+ (59%)	159Lu	7/2−#
					α (41%)	155Yb
160Hf	72	88	159.950684(12)	13.6(2) s	β+ (99.3%)	160Lu	0+
					α (.7%)	156Yb
161Hf	72	89	160.950275(24)	18.2(5) s	β+ (99.7%)	161Lu	3/2−#
					α (.3%)	157Yb
162Hf	72	90	161.94721(1)	39.4(9) s	β+ (99.99%)	162Lu	0+
					α (.008%)	158Yb
163Hf	72	91	162.94709(3)	40.0(6) s	β+	163Lu	3/2−#
					α (10−4%)	159Yb
164Hf	72	92	163.944367(22)	111(8) s	β+	164Lu	0+
165Hf	72	93	164.94457(3)	76(4) s	β+	165Lu	(5/2−)
166Hf	72	94	165.94218(3)	6.77(30) min	β+	166Lu	0+
167Hf	72	95	166.94260(3)	2.05(5) min	β+	167Lu	(5/2)−
168Hf	72	96	167.94057(3)	25.95(20) min	β+	168Lu	0+
169Hf	72	97	168.94126(3)	3.24(4) min	β+	169Lu	(5/2)−
170Hf	72	98	169.93961(3)	16.01(13) h	EC	170Lu	0+
171Hf	72	99	170.94049(3)	12.1(4) h	β+	171Lu	7/2(+)
171mHf	21.93(9) keV			29.5(9) s	IT	171Hf	1/2(−)
172Hf	72	100	171.939448(26)	1.87(3) y	EC	172Lu	0+
172mHf	2005.58(11) keV			163(3) ns			(8−)
173Hf	72	101	172.94051(3)	23.6(1) h	β+	173Lu	1/2−
174Hf[n 9]	72	102	173.940046(3)	7.0(12)×1016 y[2]	α[n 10]	170Yb	0+	0.0016(1)	0.001619–0.001621
174m1Hf	1549.3 keV			138(4) ns			(6+)
174m2Hf	1797.5(20) keV			2.39(4) μs			(8−)
174m3Hf	3311.7 keV			3.7(2) μs			(14+)
175Hf	72	103	174.941509(3)	70(2) d	β+	175Lu	5/2−
176Hf[n 11]	72	104	175.9414086(24)	Observationally Stable[n 12]			0+	0.0526(7)	0.05206–0.05271
176m1Hf	1333.07(7) keV			9.6(3) μs	IT	176Hf	6+
176m2Hf	1559.31(9) keV			9.9(2) μs	IT	176Hf	8−
176m3Hf	2865.8(7) keV			401(6) μs	IT	176Hf	14−
176m4Hf	4863.6(9) keV			43(4) μs	IT	176Hf	22−
177Hf	72	105	176.9432207(23)	Observationally Stable[n 13]			7/2−	0.1860(9)	0.18593–0.18606
177m1Hf	1315.4504(8) keV			1.09(5) s			23/2+
177m2Hf	1342.38(20) keV			55.9(12) μs			(19/2−)
177m3Hf	2740.02(15) keV			51.4(5) min			37/2−
178Hf	72	106	177.9436988(23)	Observationally Stable[n 14]			0+	0.2728(7)	0.27278–0.27297
178m1Hf	1147.423(5) keV			4.0(2) s			8−
178m2Hf	2445.69(11) keV			31(1) y			16+
178m3Hf	2573.5(5) keV			68(2) μs			(14−)
179Hf	72	107	178.9458161(23)	Observationally Stable[n 15]			9/2+	0.1362(2)	0.13619–0.1363
179m1Hf	375.0367(25) keV			18.67(4) s			1/2−
179m2Hf	1105.84(19) keV			25.05(25) d			25/2−
180Hf	72	108	179.9465500(23)	Observationally Stable[n 16]			0+	0.3508(16)	0.35076–0.351
180m1Hf	1141.48(4) keV			5.47(4) h			8−
180m2Hf	1374.15(4) keV			0.57(2) μs			(4−)
180m3Hf	2425.8(10) keV			15(5) μs			(10+)
180m4Hf	2486.3(9) keV			10(1) μs			12+
180m5Hf	2538.3(12) keV			>10 μs			(14+)
180m6Hf	3599.3(18) keV			90(10) μs			(18−)
181Hf	72	109	180.9491012(23)	42.39(6) d	β−	181Ta	1/2−
181m1Hf	595(3) keV			80(5) μs			(9/2+)
181m2Hf	1040(10) keV			~100 μs			(17/2+)
181m3Hf	1738(10) keV			1.5(5) ms			(27/2−)
182Hf	72	110	181.950554(7)	8.90(9)×106 y	β−	182Ta	0+
182mHf	1172.88(18) keV			61.5(15) min	β− (58%)	182Ta	8−
					IT (42%)	182Hf
183Hf	72	111	182.95353(3)	1.067(17) h	β−	183Ta	(3/2−)
184Hf	72	112	183.95545(4)	4.12(5) h	β−	184Ta	0+
184mHf	1272.4(4) keV			48(10) s	β−	184Ta	8−
185Hf	72	113	184.95882(21)#	3.5(6) min	β−	185Ta	3/2−#
186Hf	72	114	185.96089(32)#	2.6(12) min	β−	186Ta	0+
187Hf	72	115	186.96457(22)#	14# s [>300 ns]			9/2−#
187mHf	500(300)# keV			270(80) ns	IT	187Hf	3/2−#
188Hf	72	116	187.96690(32)#	20# s [>300 ns]			0+
189Hf	72	117	188.97085(32)#	400# ms [>300 ns]			3/2−#
190Hf	72	118	189.97338(43)#	600# ms [>300 ns]			0+
191Hf[6]	72	119
192Hf[6]	72	120					0+
This table header & footer: view

1. ^mHf – 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. Bold half-life – nearly stable, half-life longer than age of universe.
5. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
6. Modes of decay:

   EC:	Electron capture
   IT:	Isomeric transition

7. Bold symbol as daughter – Daughter product is stable.
8. ( ) spin value – Indicates spin with weak assignment arguments.
9. primordial radionuclide
10. Theorized to also undergo β⁺β⁺ decay to ¹⁷⁴Yb
11. Used in lutetium-hafnium dating
12. Believed to undergo α decay to ¹⁷²Yb
13. Believed to undergo α decay to ¹⁷³Yb
14. Believed to undergo α decay to ¹⁷⁴Yb
15. Believed to undergo α decay to ¹⁷⁵Yb
16. Believed to undergo α decay to ¹⁷⁶Yb

References

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. Caracciolo, V.; Nagorny, S.; Belli, P.; et al. (2020). "Search for α decay of naturally occurring Hf-nuclides using a Cs₂HfCl₆ scintillator". Nuclear Physics A. 1002 (121941): 121941. arXiv:2005.01373. Bibcode:2020NuPhA100221941C. doi:10.1016/j.nuclphysa.2020.121941. S2CID 218487451.
3. "Standard Atomic Weights: Hafnium". CIAAW. 2019.
4. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (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.
5. Kleine T, Walker RJ (August 2017). "Tungsten Isotopes in Planets". Annual Review of Earth and Planetary Sciences. 45 (1): 389–417. Bibcode:2017AREPS..45..389K. doi:10.1146/annurev-earth-063016-020037. PMC 6398955. PMID 30842690.
6. Haak, K.; Tarasov, O. B.; Chowdhury, P.; et al. (2023). "Production and discovery of neutron-rich isotopes by fragmentation of ¹⁹⁸Pt". Physical Review C. 108 (34608): 034608. Bibcode:2023PhRvC.108c4608H. doi:10.1103/PhysRevC.108.034608. S2CID 261649436.

• Isotope masses from:
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (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
• Isotopic compositions and standard atomic masses from:
  • 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.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (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
  • 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.