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-lifeof7.0×10¹⁶ 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]

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[edit]

Nuclide
^{[n 1]}

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

152.97069(54)#

400# ms [>200 ns]

1/2+#

^153mHf

750(100)# keV

500# ms

11/2−#

¹⁵⁴Hf

153.96486(54)#

2(1) s

β⁺

¹⁵⁴Lu

α (rare)

¹⁵⁰Yb

¹⁵⁵Hf

154.96339(43)#

890(120) ms

β⁺

¹⁵⁵Lu

7/2−#

α (rare)

¹⁵¹Yb

¹⁵⁶Hf

155.95936(22)

23(1) ms

α (97%)

¹⁵²Yb

β⁺ (3%)

¹⁵⁶Lu

^156mHf

1959.0(10) keV

480(40) μs

¹⁵⁷Hf

156.95840(21)#

115(1) ms

α (86%)

¹⁵³Yb

7/2−

β⁺ (14%)

¹⁵⁷Lu

¹⁵⁸Hf

157.954799(19)

2.84(7) s

β⁺ (55%)

¹⁵⁸Lu

α (45%)

¹⁵⁴Yb

¹⁵⁹Hf

158.953995(18)

5.20(10) s

β⁺ (59%)

¹⁵⁹Lu

7/2−#

α (41%)

¹⁵⁵Yb

¹⁶⁰Hf

159.950684(12)

13.6(2) s

β⁺ (99.3%)

¹⁶⁰Lu

α (.7%)

¹⁵⁶Yb

¹⁶¹Hf

160.950275(24)

18.2(5) s

β⁺ (99.7%)

¹⁶¹Lu

3/2−#

α (.3%)

¹⁵⁷Yb

¹⁶²Hf

161.94721(1)

39.4(9) s

β⁺ (99.99%)

¹⁶²Lu

α (.008%)

¹⁵⁸Yb

¹⁶³Hf

162.94709(3)

40.0(6) s

β⁺

¹⁶³Lu

3/2−#

α (10⁻⁴%)

¹⁵⁹Yb

¹⁶⁴Hf

163.944367(22)

111(8) s

β⁺

¹⁶⁴Lu

¹⁶⁵Hf

164.94457(3)

76(4) s

β⁺

¹⁶⁵Lu

(5/2−)

¹⁶⁶Hf

165.94218(3)

6.77(30) min

β⁺

¹⁶⁶Lu

¹⁶⁷Hf

166.94260(3)

2.05(5) min

β⁺

¹⁶⁷Lu

(5/2)−

¹⁶⁸Hf

167.94057(3)

25.95(20) min

β⁺

¹⁶⁸Lu

¹⁶⁹Hf

168.94126(3)

3.24(4) min

β⁺

¹⁶⁹Lu

(5/2)−

¹⁷⁰Hf

169.93961(3)

16.01(13) h

¹⁷⁰Lu

¹⁷¹Hf

170.94049(3)

12.1(4) h

β⁺

¹⁷¹Lu

7/2(+)

^171mHf

21.93(9) keV

29.5(9) s

¹⁷¹Hf

1/2(−)

¹⁷²Hf

100

171.939448(26)

1.87(3) y

¹⁷²Lu

^172mHf

2005.58(11) keV

163(3) ns

(8−)

¹⁷³Hf

101

172.94051(3)

23.6(1) h

β⁺

¹⁷³Lu

1/2−

¹⁷⁴Hf^{[n 9]}

102

173.940046(3)

7.0(12)×10¹⁶ y^[2]

α^{[n 10]}

¹⁷⁰Yb

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

103

174.941509(3)

70(2) d

β⁺

¹⁷⁵Lu

5/2−

¹⁷⁶Hf^{[n 11]}

104

175.9414086(24)

Observationally Stable^{[n 12]}

0.0526(7)

0.05206–0.05271

^176m1Hf

1333.07(7) keV

9.6(3) μs

¹⁷⁶Hf

^176m2Hf

1559.31(9) keV

9.9(2) μs

¹⁷⁶Hf

8−

^176m3Hf

2865.8(7) keV

401(6) μs

¹⁷⁶Hf

14−

^176m4Hf

4863.6(9) keV

43(4) μs

¹⁷⁶Hf

22−

¹⁷⁷Hf

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

106

177.9436988(23)

Observationally Stable^{[n 14]}

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

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

108

179.9465500(23)

Observationally Stable^{[n 16]}

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

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

110

181.950554(7)

8.90(9)×10⁶ y

β⁻

¹⁸²Ta

^182mHf

1172.88(18) keV

61.5(15) min

β⁻ (58%)

¹⁸²Ta

8−

IT (42%)

¹⁸²Hf

¹⁸³Hf

111

182.95353(3)

1.067(17) h

β⁻

¹⁸³Ta

(3/2−)

¹⁸⁴Hf

112

183.95545(4)

4.12(5) h

β⁻

¹⁸⁴Ta

^184mHf

1272.4(4) keV

48(10) s

β⁻

¹⁸⁴Ta

8−

¹⁸⁵Hf

113

184.95882(21)#

3.5(6) min

β⁻

¹⁸⁵Ta

3/2−#

¹⁸⁶Hf

114

185.96089(32)#

2.6(12) min

β⁻

¹⁸⁶Ta

¹⁸⁷Hf

115

186.96457(22)#

14# s [>300 ns]

9/2−#

^187mHf

500(300)# keV

270(80) ns

¹⁸⁷Hf

3/2−#

¹⁸⁸Hf

116

187.96690(32)#

20# s [>300 ns]

¹⁸⁹Hf

117

188.97085(32)#

400# ms [>300 ns]

3/2−#

¹⁹⁰Hf

118

189.97338(43)#

600# ms [>300 ns]

¹⁹¹Hf^[6]

119

¹⁹²Hf^[6]

120

This table header & footer:

^ ^mHf – 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).

^ Bold half-life – nearly stable, half-life longer than age of universe.

^ ^a ^b ^c # – 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

^ Bold symbol as daughter – Daughter product is stable.

^ ( ) spin value – Indicates spin with weak assignment arguments.

^ primordial radionuclide

^ Theorized to also undergo β⁺β⁺ decay to ¹⁷⁴Yb

^ Used in lutetium-hafnium dating

^ Believed to undergo α decay to ¹⁷²Yb

^ Believed to undergo α decay to ¹⁷³Yb

^ Believed to undergo α decay to ¹⁷⁴Yb

^ Believed to undergo α decay to ¹⁷⁵Yb

^ Believed to undergo α decay to ¹⁷⁶Yb

References[edit]

^ 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.

^ ^a ^b ^c 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.

^ "Standard Atomic Weights: Hafnium". CIAAW. 2019.

^ 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.

^ 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.

^ ^a ^b 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.