Hafnium-176

Natural hafnium (Hf) consists of five stable isotopes (¹⁷⁶Hf, ¹⁷⁷Hf, ¹⁷⁸Hf, ¹⁷⁹Hf, and ¹⁸⁰Hf) and one very long-lived radioisotope, ¹⁷⁴Hf, with a half-life of 2×10¹⁵ years. In addition, there are 30 other known radionuclides, the most stable of which is ¹⁸²Hf with a half-life of 8.9×10⁶ years. No other radioisotope has a half-life over 1.87 days. Most isotopes have half-lives under 1 minute. There are also 26 known nuclear isomers, the most stable of which is ^178m2Hf with a half-life of 31 years.

Relative atomic mass: 178.49(2).

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