Nuclides with atomic number of 72 but with different mass numbers
Natural hafnium (72 Hf) consists of five observationally stable isotopes (176 Hf, 177 Hf, 178 Hf, 179 Hf, and 180 Hf) and one very long-lived radioisotope , 174 Hf, with a half-life of 7.0× 1016 years.[ 2] In addition, there are 34 known synthetic radioisotopes , the most stable of which is 182 Hf 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 178m2 Hf 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.
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